diff --git a/news/f14947e7-deea-4e17-bdc2-dd8dab2a1fa5.trivial.rst b/news/f14947e7-deea-4e17-bdc2-dd8dab2a1fa5.trivial.rst
new file mode 100644
index 00000000000..001cec34342
--- /dev/null
+++ b/news/f14947e7-deea-4e17-bdc2-dd8dab2a1fa5.trivial.rst
@@ -0,0 +1,5 @@
+Convert numerous internal classes to dataclasses for readability and stricter
+enforcement of immutability across the codebase. A conservative approach was
+taken in selecting which classes to convert. Classes which did not convert
+cleanly into a dataclass or were "too complex" (e.g. maintains interconnected
+state) were left alone.
diff --git a/src/pip/_internal/index/collector.py b/src/pip/_internal/index/collector.py
index a22e3b91fcb..5f8fdee3d46 100644
--- a/src/pip/_internal/index/collector.py
+++ b/src/pip/_internal/index/collector.py
@@ -11,6 +11,7 @@
 import os
 import urllib.parse
 import urllib.request
+from dataclasses import dataclass
 from html.parser import HTMLParser
 from optparse import Values
 from typing import (
@@ -248,29 +249,22 @@ def parse_links(page: "IndexContent") -> Iterable[Link]:
         yield link
 
 
+@dataclass(frozen=True)
 class IndexContent:
-    """Represents one response (or page), along with its URL"""
+    """Represents one response (or page), along with its URL.
 
-    def __init__(
-        self,
-        content: bytes,
-        content_type: str,
-        encoding: Optional[str],
-        url: str,
-        cache_link_parsing: bool = True,
-    ) -> None:
-        """
-        :param encoding: the encoding to decode the given content.
-        :param url: the URL from which the HTML was downloaded.
-        :param cache_link_parsing: whether links parsed from this page's url
-                                   should be cached. PyPI index urls should
-                                   have this set to False, for example.
-        """
-        self.content = content
-        self.content_type = content_type
-        self.encoding = encoding
-        self.url = url
-        self.cache_link_parsing = cache_link_parsing
+    :param encoding: the encoding to decode the given content.
+    :param url: the URL from which the HTML was downloaded.
+    :param cache_link_parsing: whether links parsed from this page's url
+                               should be cached. PyPI index urls should
+                               have this set to False, for example.
+    """
+
+    content: bytes
+    content_type: str
+    encoding: Optional[str]
+    url: str
+    cache_link_parsing: bool = True
 
     def __str__(self) -> str:
         return redact_auth_from_url(self.url)
diff --git a/src/pip/_internal/index/package_finder.py b/src/pip/_internal/index/package_finder.py
index b5b9679f246..98ee6315567 100644
--- a/src/pip/_internal/index/package_finder.py
+++ b/src/pip/_internal/index/package_finder.py
@@ -5,6 +5,7 @@
 import itertools
 import logging
 import re
+from dataclasses import dataclass
 from typing import TYPE_CHECKING, FrozenSet, Iterable, List, Optional, Set, Tuple, Union
 
 from pip._vendor.packaging import specifiers
@@ -322,22 +323,15 @@ def filter_unallowed_hashes(
     return filtered
 
 
+@dataclass
 class CandidatePreferences:
     """
     Encapsulates some of the preferences for filtering and sorting
     InstallationCandidate objects.
     """
 
-    def __init__(
-        self,
-        prefer_binary: bool = False,
-        allow_all_prereleases: bool = False,
-    ) -> None:
-        """
-        :param allow_all_prereleases: Whether to allow all pre-releases.
-        """
-        self.allow_all_prereleases = allow_all_prereleases
-        self.prefer_binary = prefer_binary
+    prefer_binary: bool = False
+    allow_all_prereleases: bool = False
 
 
 class BestCandidateResult:
diff --git a/src/pip/_internal/locations/_sysconfig.py b/src/pip/_internal/locations/_sysconfig.py
index 97aef1f1ac2..ca860ea562c 100644
--- a/src/pip/_internal/locations/_sysconfig.py
+++ b/src/pip/_internal/locations/_sysconfig.py
@@ -192,9 +192,10 @@ def get_scheme(
         data=paths["data"],
     )
     if root is not None:
+        converted_keys = {}
         for key in SCHEME_KEYS:
-            value = change_root(root, getattr(scheme, key))
-            setattr(scheme, key, value)
+            converted_keys[key] = change_root(root, getattr(scheme, key))
+        scheme = Scheme(**converted_keys)
     return scheme
 
 
diff --git a/src/pip/_internal/models/candidate.py b/src/pip/_internal/models/candidate.py
index b12ffeeac4a..f27f283154a 100644
--- a/src/pip/_internal/models/candidate.py
+++ b/src/pip/_internal/models/candidate.py
@@ -1,28 +1,25 @@
+from dataclasses import dataclass
+
+from pip._vendor.packaging.version import Version
 from pip._vendor.packaging.version import parse as parse_version
 
 from pip._internal.models.link import Link
-from pip._internal.utils.models import KeyBasedCompareMixin
 
 
-class InstallationCandidate(KeyBasedCompareMixin):
+@dataclass(frozen=True)
+class InstallationCandidate:
     """Represents a potential "candidate" for installation."""
 
     __slots__ = ["name", "version", "link"]
 
+    name: str
+    version: Version
+    link: Link
+
     def __init__(self, name: str, version: str, link: Link) -> None:
-        self.name = name
-        self.version = parse_version(version)
-        self.link = link
-
-        super().__init__(
-            key=(self.name, self.version, self.link),
-            defining_class=InstallationCandidate,
-        )
-
-    def __repr__(self) -> str:
-        return (
-            f"<InstallationCandidate({self.name!r}, {self.version!r}, {self.link!r})>"
-        )
+        object.__setattr__(self, "name", name)
+        object.__setattr__(self, "version", parse_version(version))
+        object.__setattr__(self, "link", link)
 
     def __str__(self) -> str:
         return f"{self.name!r} candidate (version {self.version} at {self.link})"
diff --git a/src/pip/_internal/models/direct_url.py b/src/pip/_internal/models/direct_url.py
index 1063952489a..fc5ec8d4aa9 100644
--- a/src/pip/_internal/models/direct_url.py
+++ b/src/pip/_internal/models/direct_url.py
@@ -3,7 +3,8 @@
 import json
 import re
 import urllib.parse
-from typing import Any, Dict, Iterable, Optional, Type, TypeVar, Union
+from dataclasses import dataclass
+from typing import Any, ClassVar, Dict, Iterable, Optional, Type, TypeVar, Union
 
 __all__ = [
     "DirectUrl",
@@ -65,18 +66,13 @@ def _filter_none(**kwargs: Any) -> Dict[str, Any]:
     return {k: v for k, v in kwargs.items() if v is not None}
 
 
+@dataclass
 class VcsInfo:
-    name = "vcs_info"
+    name: ClassVar = "vcs_info"
 
-    def __init__(
-        self,
-        vcs: str,
-        commit_id: str,
-        requested_revision: Optional[str] = None,
-    ) -> None:
-        self.vcs = vcs
-        self.requested_revision = requested_revision
-        self.commit_id = commit_id
+    vcs: str
+    commit_id: str
+    requested_revision: Optional[str] = None
 
     @classmethod
     def _from_dict(cls, d: Optional[Dict[str, Any]]) -> Optional["VcsInfo"]:
@@ -140,14 +136,11 @@ def _to_dict(self) -> Dict[str, Any]:
         return _filter_none(hash=self.hash, hashes=self.hashes)
 
 
+@dataclass
 class DirInfo:
-    name = "dir_info"
+    name: ClassVar = "dir_info"
 
-    def __init__(
-        self,
-        editable: bool = False,
-    ) -> None:
-        self.editable = editable
+    editable: bool = False
 
     @classmethod
     def _from_dict(cls, d: Optional[Dict[str, Any]]) -> Optional["DirInfo"]:
@@ -162,16 +155,11 @@ def _to_dict(self) -> Dict[str, Any]:
 InfoType = Union[ArchiveInfo, DirInfo, VcsInfo]
 
 
+@dataclass
 class DirectUrl:
-    def __init__(
-        self,
-        url: str,
-        info: InfoType,
-        subdirectory: Optional[str] = None,
-    ) -> None:
-        self.url = url
-        self.info = info
-        self.subdirectory = subdirectory
+    url: str
+    info: InfoType
+    subdirectory: Optional[str] = None
 
     def _remove_auth_from_netloc(self, netloc: str) -> str:
         if "@" not in netloc:
diff --git a/src/pip/_internal/models/link.py b/src/pip/_internal/models/link.py
index 73041b864c3..2f41f2f6a09 100644
--- a/src/pip/_internal/models/link.py
+++ b/src/pip/_internal/models/link.py
@@ -27,7 +27,6 @@
     split_auth_from_netloc,
     splitext,
 )
-from pip._internal.utils.models import KeyBasedCompareMixin
 from pip._internal.utils.urls import path_to_url, url_to_path
 
 if TYPE_CHECKING:
@@ -179,7 +178,8 @@ def _ensure_quoted_url(url: str) -> str:
     return urllib.parse.urlunparse(result._replace(path=path))
 
 
-class Link(KeyBasedCompareMixin):
+@functools.total_ordering
+class Link:
     """Represents a parsed link from a Package Index's simple URL"""
 
     __slots__ = [
@@ -254,8 +254,6 @@ def __init__(
         self.yanked_reason = yanked_reason
         self.metadata_file_data = metadata_file_data
 
-        super().__init__(key=url, defining_class=Link)
-
         self.cache_link_parsing = cache_link_parsing
         self.egg_fragment = self._egg_fragment()
 
@@ -375,6 +373,19 @@ def __str__(self) -> str:
     def __repr__(self) -> str:
         return f"<Link {self}>"
 
+    def __hash__(self) -> int:
+        return hash(self.url)
+
+    def __eq__(self, other: Any) -> bool:
+        if not isinstance(other, Link):
+            return NotImplemented
+        return self.url == other.url
+
+    def __lt__(self, other: Any) -> bool:
+        if not isinstance(other, Link):
+            return NotImplemented
+        return self.url < other.url
+
     @property
     def url(self) -> str:
         return self._url
diff --git a/src/pip/_internal/models/scheme.py b/src/pip/_internal/models/scheme.py
index 9d804a67371..06a9a550e34 100644
--- a/src/pip/_internal/models/scheme.py
+++ b/src/pip/_internal/models/scheme.py
@@ -5,9 +5,12 @@
 https://docs.python.org/3/install/index.html#alternate-installation.
 """
 
+from dataclasses import dataclass
+
 SCHEME_KEYS = ["platlib", "purelib", "headers", "scripts", "data"]
 
 
+@dataclass(frozen=True)
 class Scheme:
     """A Scheme holds paths which are used as the base directories for
     artifacts associated with a Python package.
@@ -15,16 +18,8 @@ class Scheme:
 
     __slots__ = SCHEME_KEYS
 
-    def __init__(
-        self,
-        platlib: str,
-        purelib: str,
-        headers: str,
-        scripts: str,
-        data: str,
-    ) -> None:
-        self.platlib = platlib
-        self.purelib = purelib
-        self.headers = headers
-        self.scripts = scripts
-        self.data = data
+    platlib: str
+    purelib: str
+    headers: str
+    scripts: str
+    data: str
diff --git a/src/pip/_internal/models/search_scope.py b/src/pip/_internal/models/search_scope.py
index a96ddcb4096..ee7bc86229a 100644
--- a/src/pip/_internal/models/search_scope.py
+++ b/src/pip/_internal/models/search_scope.py
@@ -3,6 +3,7 @@
 import os
 import posixpath
 import urllib.parse
+from dataclasses import dataclass
 from typing import List
 
 from pip._vendor.packaging.utils import canonicalize_name
@@ -14,6 +15,7 @@
 logger = logging.getLogger(__name__)
 
 
+@dataclass(frozen=True)
 class SearchScope:
     """
     Encapsulates the locations that pip is configured to search.
@@ -21,6 +23,10 @@ class SearchScope:
 
     __slots__ = ["find_links", "index_urls", "no_index"]
 
+    find_links: List[str]
+    index_urls: List[str]
+    no_index: bool
+
     @classmethod
     def create(
         cls,
@@ -63,16 +69,6 @@ def create(
             no_index=no_index,
         )
 
-    def __init__(
-        self,
-        find_links: List[str],
-        index_urls: List[str],
-        no_index: bool,
-    ) -> None:
-        self.find_links = find_links
-        self.index_urls = index_urls
-        self.no_index = no_index
-
     def get_formatted_locations(self) -> str:
         lines = []
         redacted_index_urls = []
diff --git a/src/pip/_internal/models/selection_prefs.py b/src/pip/_internal/models/selection_prefs.py
index 977bc4caa75..e9b50aa5175 100644
--- a/src/pip/_internal/models/selection_prefs.py
+++ b/src/pip/_internal/models/selection_prefs.py
@@ -3,6 +3,8 @@
 from pip._internal.models.format_control import FormatControl
 
 
+# TODO: This needs Python 3.10's improved slots support for dataclasses
+# to be converted into a dataclass.
 class SelectionPreferences:
     """
     Encapsulates the candidate selection preferences for downloading
diff --git a/src/pip/_internal/operations/prepare.py b/src/pip/_internal/operations/prepare.py
index 956717d1e52..e6aa3447200 100644
--- a/src/pip/_internal/operations/prepare.py
+++ b/src/pip/_internal/operations/prepare.py
@@ -7,6 +7,7 @@
 import mimetypes
 import os
 import shutil
+from dataclasses import dataclass
 from pathlib import Path
 from typing import Dict, Iterable, List, Optional
 
@@ -80,13 +81,14 @@ def unpack_vcs_link(link: Link, location: str, verbosity: int) -> None:
     vcs_backend.unpack(location, url=hide_url(link.url), verbosity=verbosity)
 
 
+@dataclass
 class File:
-    def __init__(self, path: str, content_type: Optional[str]) -> None:
-        self.path = path
-        if content_type is None:
-            self.content_type = mimetypes.guess_type(path)[0]
-        else:
-            self.content_type = content_type
+    path: str
+    content_type: Optional[str] = None
+
+    def __post_init__(self) -> None:
+        if self.content_type is None:
+            self.content_type = mimetypes.guess_type(self.path)[0]
 
 
 def get_http_url(
diff --git a/src/pip/_internal/req/__init__.py b/src/pip/_internal/req/__init__.py
index 16de903a44c..422d851d729 100644
--- a/src/pip/_internal/req/__init__.py
+++ b/src/pip/_internal/req/__init__.py
@@ -1,5 +1,6 @@
 import collections
 import logging
+from dataclasses import dataclass
 from typing import Generator, List, Optional, Sequence, Tuple
 
 from pip._internal.utils.logging import indent_log
@@ -18,12 +19,9 @@
 logger = logging.getLogger(__name__)
 
 
+@dataclass(frozen=True)
 class InstallationResult:
-    def __init__(self, name: str) -> None:
-        self.name = name
-
-    def __repr__(self) -> str:
-        return f"InstallationResult(name={self.name!r})"
+    name: str
 
 
 def _validate_requirements(
diff --git a/src/pip/_internal/req/constructors.py b/src/pip/_internal/req/constructors.py
index 74296345620..36f517e599d 100644
--- a/src/pip/_internal/req/constructors.py
+++ b/src/pip/_internal/req/constructors.py
@@ -12,6 +12,7 @@
 import logging
 import os
 import re
+from dataclasses import dataclass
 from typing import Collection, Dict, List, Optional, Set, Tuple, Union
 
 from pip._vendor.packaging.markers import Marker
@@ -191,18 +192,12 @@ def deduce_helpful_msg(req: str) -> str:
     return msg
 
 
+@dataclass(frozen=True)
 class RequirementParts:
-    def __init__(
-        self,
-        requirement: Optional[Requirement],
-        link: Optional[Link],
-        markers: Optional[Marker],
-        extras: Set[str],
-    ):
-        self.requirement = requirement
-        self.link = link
-        self.markers = markers
-        self.extras = extras
+    requirement: Optional[Requirement]
+    link: Optional[Link]
+    markers: Optional[Marker]
+    extras: Set[str]
 
 
 def parse_req_from_editable(editable_req: str) -> RequirementParts:
diff --git a/src/pip/_internal/resolution/resolvelib/base.py b/src/pip/_internal/resolution/resolvelib/base.py
index 9c0ef5ca7b9..4269c7fbecc 100644
--- a/src/pip/_internal/resolution/resolvelib/base.py
+++ b/src/pip/_internal/resolution/resolvelib/base.py
@@ -1,3 +1,4 @@
+from dataclasses import dataclass
 from typing import FrozenSet, Iterable, Optional, Tuple, Union
 
 from pip._vendor.packaging.specifiers import SpecifierSet
@@ -19,13 +20,11 @@ def format_name(project: NormalizedName, extras: FrozenSet[NormalizedName]) -> s
     return f"{project}[{extras_expr}]"
 
 
+@dataclass(frozen=True)
 class Constraint:
-    def __init__(
-        self, specifier: SpecifierSet, hashes: Hashes, links: FrozenSet[Link]
-    ) -> None:
-        self.specifier = specifier
-        self.hashes = hashes
-        self.links = links
+    specifier: SpecifierSet
+    hashes: Hashes
+    links: FrozenSet[Link]
 
     @classmethod
     def empty(cls) -> "Constraint":
diff --git a/src/pip/_internal/utils/misc.py b/src/pip/_internal/utils/misc.py
index 1ad3f6162a2..a5d17565812 100644
--- a/src/pip/_internal/utils/misc.py
+++ b/src/pip/_internal/utils/misc.py
@@ -11,6 +11,7 @@
 import sys
 import sysconfig
 import urllib.parse
+from dataclasses import dataclass
 from functools import partial
 from io import StringIO
 from itertools import filterfalse, tee, zip_longest
@@ -580,10 +581,10 @@ def redact_auth_from_requirement(req: Requirement) -> str:
     return str(req).replace(req.url, redact_auth_from_url(req.url))
 
 
+@dataclass(frozen=True)
 class HiddenText:
-    def __init__(self, secret: str, redacted: str) -> None:
-        self.secret = secret
-        self.redacted = redacted
+    secret: str
+    redacted: str
 
     def __repr__(self) -> str:
         return f"<HiddenText {str(self)!r}>"
diff --git a/src/pip/_internal/utils/models.py b/src/pip/_internal/utils/models.py
deleted file mode 100644
index b6bb21a8b26..00000000000
--- a/src/pip/_internal/utils/models.py
+++ /dev/null
@@ -1,39 +0,0 @@
-"""Utilities for defining models
-"""
-
-import operator
-from typing import Any, Callable, Type
-
-
-class KeyBasedCompareMixin:
-    """Provides comparison capabilities that is based on a key"""
-
-    __slots__ = ["_compare_key", "_defining_class"]
-
-    def __init__(self, key: Any, defining_class: Type["KeyBasedCompareMixin"]) -> None:
-        self._compare_key = key
-        self._defining_class = defining_class
-
-    def __hash__(self) -> int:
-        return hash(self._compare_key)
-
-    def __lt__(self, other: Any) -> bool:
-        return self._compare(other, operator.__lt__)
-
-    def __le__(self, other: Any) -> bool:
-        return self._compare(other, operator.__le__)
-
-    def __gt__(self, other: Any) -> bool:
-        return self._compare(other, operator.__gt__)
-
-    def __ge__(self, other: Any) -> bool:
-        return self._compare(other, operator.__ge__)
-
-    def __eq__(self, other: Any) -> bool:
-        return self._compare(other, operator.__eq__)
-
-    def _compare(self, other: Any, method: Callable[[Any, Any], bool]) -> bool:
-        if not isinstance(other, self._defining_class):
-            return NotImplemented
-
-        return method(self._compare_key, other._compare_key)
diff --git a/src/pip/_internal/vcs/git.py b/src/pip/_internal/vcs/git.py
index 8c242cf8956..0425debb3ae 100644
--- a/src/pip/_internal/vcs/git.py
+++ b/src/pip/_internal/vcs/git.py
@@ -4,6 +4,7 @@
 import re
 import urllib.parse
 import urllib.request
+from dataclasses import replace
 from typing import List, Optional, Tuple
 
 from pip._internal.exceptions import BadCommand, InstallationError
@@ -217,7 +218,7 @@ def resolve_revision(
 
         if sha is not None:
             rev_options = rev_options.make_new(sha)
-            rev_options.branch_name = rev if is_branch else None
+            rev_options = replace(rev_options, branch_name=(rev if is_branch else None))
 
             return rev_options
 
diff --git a/src/pip/_internal/vcs/versioncontrol.py b/src/pip/_internal/vcs/versioncontrol.py
index 7eef8ec898e..ce9cf112d31 100644
--- a/src/pip/_internal/vcs/versioncontrol.py
+++ b/src/pip/_internal/vcs/versioncontrol.py
@@ -5,6 +5,7 @@
 import shutil
 import sys
 import urllib.parse
+from dataclasses import dataclass, field
 from typing import (
     Any,
     Dict,
@@ -114,33 +115,22 @@ def __init__(self, url: str):
         self.url = url
 
 
+@dataclass(frozen=True)
 class RevOptions:
     """
     Encapsulates a VCS-specific revision to install, along with any VCS
     install options.
 
-    Instances of this class should be treated as if immutable.
+    Args:
+        vc_class: a VersionControl subclass.
+        rev: the name of the revision to install.
+        extra_args: a list of extra options.
     """
 
-    def __init__(
-        self,
-        vc_class: Type["VersionControl"],
-        rev: Optional[str] = None,
-        extra_args: Optional[CommandArgs] = None,
-    ) -> None:
-        """
-        Args:
-          vc_class: a VersionControl subclass.
-          rev: the name of the revision to install.
-          extra_args: a list of extra options.
-        """
-        if extra_args is None:
-            extra_args = []
-
-        self.extra_args = extra_args
-        self.rev = rev
-        self.vc_class = vc_class
-        self.branch_name: Optional[str] = None
+    vc_class: Type["VersionControl"]
+    rev: Optional[str] = None
+    extra_args: CommandArgs = field(default_factory=list)
+    branch_name: Optional[str] = None
 
     def __repr__(self) -> str:
         return f"<RevOptions {self.vc_class.name}: rev={self.rev!r}>"
@@ -354,7 +344,7 @@ def make_rev_options(
           rev: the name of a revision to install.
           extra_args: a list of extra options.
         """
-        return RevOptions(cls, rev, extra_args=extra_args)
+        return RevOptions(cls, rev, extra_args=extra_args or [])
 
     @classmethod
     def _is_local_repository(cls, repo: str) -> bool:
diff --git a/tests/unit/test_models.py b/tests/unit/test_models.py
index c5545e37d01..2550cae412d 100644
--- a/tests/unit/test_models.py
+++ b/tests/unit/test_models.py
@@ -49,11 +49,3 @@ def test_sets_correct_variables(self) -> None:
         assert obj.name == "A"
         assert obj.version == parse_version("1.0.0")
         assert obj.link.url == "https://somewhere.com/path/A-1.0.0.tar.gz"
-
-    # NOTE: This isn't checking the ordering logic; only the data provided to
-    #       it is correct.
-    def test_sets_the_right_key(self) -> None:
-        obj = candidate.InstallationCandidate(
-            "A", "1.0.0", Link("https://somewhere.com/path/A-1.0.0.tar.gz")
-        )
-        assert obj._compare_key == (obj.name, obj.version, obj.link)