diff --git a/README.md b/README.md
index fadf5c8..4544538 100644
--- a/README.md
+++ b/README.md
@@ -693,6 +693,41 @@ An error is displayed if the specified extended regular expression is invalid.
 This option and partial matching (`--partial` or `-p`) are mutually exclusive.
 An error is displayed when used simultaneously.
 
+### `assert_regex`
+
+This function is similar to `assert_equal` but uses pattern matching instead of
+equality, by wrapping `[[ value =~ pattern ]]`.
+
+Fail if the value (first parameter) does not match the pattern (second
+parameter).
+
+```bash
+@test 'assert_regex()' {
+  assert_regex 'what' 'x$'
+}
+```
+
+On failure, the value and the pattern are displayed.
+
+```
+-- values does not match regular expression --
+value    : what
+pattern  : x$
+--
+```
+
+If the value is longer than one line then it is displayed in *multi-line*
+format.
+
+An error is displayed if the specified extended regular expression is invalid.
+
+For description of the matching behavior, refer to the documentation of the
+`=~` operator in the
+[Bash manual]: https://www.gnu.org/software/bash/manual/html_node/Conditional-Constructs.html.
+Note that the `BASH_REMATCH` array is available immediately after the
+assertion succeeds but is fragile, i.e. prone to being overwritten as a side
+effect of other actions.
+
 <!-- REFERENCES -->
 
 [bats]: https://github.com/bats-core/bats-core
diff --git a/load.bash b/load.bash
index 1201df1..a5fe0f2 100644
--- a/load.bash
+++ b/load.bash
@@ -29,3 +29,4 @@ source "$(dirname "${BASH_SOURCE[0]}")/src/assert_output.bash"
 source "$(dirname "${BASH_SOURCE[0]}")/src/refute_output.bash"
 source "$(dirname "${BASH_SOURCE[0]}")/src/assert_line.bash"
 source "$(dirname "${BASH_SOURCE[0]}")/src/refute_line.bash"
+source "$(dirname "${BASH_SOURCE[0]}")/src/assert_regex.bash"
diff --git a/src/assert_regex.bash b/src/assert_regex.bash
new file mode 100644
index 0000000..636318e
--- /dev/null
+++ b/src/assert_regex.bash
@@ -0,0 +1,56 @@
+# `assert_regex`
+#
+# This function is similar to `assert_equal` but uses pattern matching instead
+# of equality, by wrapping `[[ value =~ pattern ]]`.
+#
+# Fail if the value (first parameter) does not match the pattern (second
+# parameter).
+#
+# ```bash
+# @test 'assert_regex()' {
+#   assert_regex 'what' 'x$'
+# }
+# ```
+#
+# On failure, the value and the pattern are displayed.
+#
+# ```
+# -- values does not match regular expression --
+# value    : what
+# pattern  : x$
+# --
+# ```
+#
+# If the value is longer than one line then it is displayed in *multi-line*
+# format.
+#
+# An error is displayed if the specified extended regular expression is invalid.
+#
+# For description of the matching behavior, refer to the documentation of the
+# `=~` operator in the
+# [Bash manual]: https://www.gnu.org/software/bash/manual/html_node/Conditional-Constructs.html.
+# Note that the `BASH_REMATCH` array is available immediately after the
+# assertion succeeds but is fragile, i.e. prone to being overwritten as a side
+# effect of other actions.
+assert_regex() {
+	local -r value="${1}"
+	local -r pattern="${2}"
+
+	if [[ '' =~ ${pattern} ]] || (( ${?} == 2 )); then
+		echo "Invalid extended regular expression: \`${pattern}'" \
+		| batslib_decorate 'ERROR: assert_regex' \
+		| fail
+	elif ! [[ "${value}" =~ ${pattern} ]]; then
+		if shopt -p nocasematch &>/dev/null; then
+			local case_sensitive=insensitive
+		else
+			local case_sensitive=sensitive
+		fi
+		batslib_print_kv_single_or_multi 8 \
+			'value' "${value}" \
+			'pattern'  "${pattern}" \
+			'case' "${case_sensitive}" \
+		| batslib_decorate 'value does not match regular expression' \
+		| fail
+	fi
+}
diff --git a/test/assert_regex.bats b/test/assert_regex.bats
new file mode 100644
index 0000000..ef9c3a8
--- /dev/null
+++ b/test/assert_regex.bats
@@ -0,0 +1,82 @@
+#!/usr/bin/env bats
+
+load test_helper
+
+#
+# Literal matching
+#
+
+# Correctness
+@test "assert_regex() <value> <pattern>: succeeds if a <value> substring matches extended regular expression <pattern>" {
+  run assert_regex 'abc' '^[a-z]b[c-z]+'
+  assert_test_pass
+}
+
+@test "assert_regex() <value> <pattern>: fails if no <value> substring matches extended regular expression <pattern>" {
+  run assert_regex 'bcd' '^[a-z]b[c-z]+'
+  assert_test_fail <<'ERR_MSG'
+
+-- value does not match regular expression --
+value    : bcd
+pattern  : ^[a-z]b[c-z]+
+case     : sensitive
+--
+ERR_MSG
+}
+
+@test "assert_regex() <value> <pattern>: provides results in BASH_REMATCH" {
+  unset -v BASH_REMATCH
+
+  assert_regex 'abcd' 'b.d'
+  declare -p BASH_REMATCH
+  [ "${BASH_REMATCH[0]}" = 'bcd' ]
+}
+
+@test "assert_regex() <value> <pattern>: matches case-insensitively when 'nocasematch' is set" {
+  shopt -s nocasematch
+
+  assert_regex 'aBc' 'ABC'
+}
+
+@test "assert_regex() <value> <pattern>: outputs multi-line <value> nicely when it fails" {
+  run assert_regex $'bcd\n123' '^[a-z]b[c-z]+'
+  assert_test_fail <<'ERR_MSG'
+
+-- value does not match regular expression --
+value (2 lines):
+  bcd
+  123
+pattern (1 lines):
+  ^[a-z]b[c-z]+
+case (1 lines):
+  sensitive
+--
+ERR_MSG
+
+  shopt -s nocasematch
+  run assert_regex $'bcd\n123' '^[a-z]b[c-z]+'
+  assert_test_fail <<'ERR_MSG'
+
+-- value does not match regular expression --
+value (2 lines):
+  bcd
+  123
+pattern (1 lines):
+  ^[a-z]b[c-z]+
+case (1 lines):
+  insensitive
+--
+ERR_MSG
+}
+
+# Error handling
+@test "assert_regex() <value> <pattern>: returns 1 and displays an error message if <pattern> is not a valid extended regular expression" {
+  run assert_regex value '[.*'
+
+  assert_test_fail <<'ERR_MSG'
+
+-- ERROR: assert_regex --
+Invalid extended regular expression: `[.*'
+--
+ERR_MSG
+}