diff --git a/CHANGELOG.next.toml b/CHANGELOG.next.toml
index 63c22df5e8..468c033fae 100644
--- a/CHANGELOG.next.toml
+++ b/CHANGELOG.next.toml
@@ -102,3 +102,15 @@ message = "Required members with @contextParam are now treated as client-side re
 references = ["smithy-rs#2964"]
 meta = { "breaking" = false, "tada" = false, "bug" = false, target = "client" }
 author = "rcoh"
+
+[[aws-sdk-rust]]
+message = "Remove `once_cell` from public API"
+references = ["smithy-rs#2973"]
+meta = { "breaking" = true, "tada" = false, "bug" = false }
+author = "ysaito1001"
+
+[[smithy-rs]]
+message = "Remove `once_cell` from public API"
+references = ["smithy-rs#2973"]
+meta = { "breaking" = true, "tada" = false, "bug" = false, "target" = "all" }
+author = "ysaito1001"
diff --git a/rust-runtime/aws-smithy-http/external-types.toml b/rust-runtime/aws-smithy-http/external-types.toml
index a228978c9a..cf745485bb 100644
--- a/rust-runtime/aws-smithy-http/external-types.toml
+++ b/rust-runtime/aws-smithy-http/external-types.toml
@@ -26,9 +26,6 @@ allowed_external_types = [
     # TODO(https://github.com/awslabs/smithy-rs/issues/1193): Feature gate references to Tokio `File`
     "tokio::fs::file::File",
 
-    # TODO(https://github.com/awslabs/smithy-rs/issues/1193): Don't expose `once_cell` in public API
-    "once_cell::sync::Lazy",
-
     # TODO(https://github.com/awslabs/smithy-rs/issues/1193): Once tooling permits it, only allow the following types in the `event-stream` feature
     "aws_smithy_eventstream::*",
 ]
diff --git a/rust-runtime/aws-smithy-http/src/http_versions.rs b/rust-runtime/aws-smithy-http/src/http_versions.rs
deleted file mode 100644
index 4f4373589f..0000000000
--- a/rust-runtime/aws-smithy-http/src/http_versions.rs
+++ /dev/null
@@ -1,17 +0,0 @@
-/*
- * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
- * SPDX-License-Identifier: Apache-2.0
- */
-
-//! HTTP Version-related code
-
-use http::Version as HttpVersion;
-use once_cell::sync::Lazy;
-
-/// A list of supported or desired HttpVersions. Typically use when requesting an HTTP Client from a
-/// client cache.
-pub type HttpVersionList = Vec<HttpVersion>;
-
-/// The default list of desired HTTP protocol versions to use when making requests
-pub static DEFAULT_HTTP_VERSION_LIST: Lazy<HttpVersionList> =
-    Lazy::new(|| vec![HttpVersion::HTTP_11]);
diff --git a/rust-runtime/aws-smithy-http/src/lib.rs b/rust-runtime/aws-smithy-http/src/lib.rs
index ad53e37f9c..b24ecd3bf1 100644
--- a/rust-runtime/aws-smithy-http/src/lib.rs
+++ b/rust-runtime/aws-smithy-http/src/lib.rs
@@ -29,7 +29,6 @@ pub mod body;
 pub mod endpoint;
 pub mod header;
 pub mod http;
-pub mod http_versions;
 pub mod label;
 pub mod middleware;
 pub mod operation;