diff --git a/llvm/utils/lit/lit/TestRunner.py b/llvm/utils/lit/lit/TestRunner.py
index da7fa86fd3917..c96b7927dd37c 100644
--- a/llvm/utils/lit/lit/TestRunner.py
+++ b/llvm/utils/lit/lit/TestRunner.py
@@ -570,6 +570,14 @@ def executeBuiltinColon(cmd, cmd_shenv):
     return ShellCommandResult(cmd, "", "", 0, False)
 
 
+def executeBuiltinUnset(cmd, shenv):
+    """executeBuiltinUnset - Handle the 'unset' command."""
+    raise InternalShellError(
+        cmd,
+        "'unset' command is not supported by the lit internal shell. Please use 'env -u VARIABLE' to unset environment variables.",
+    )
+
+
 def processRedirects(cmd, stdin_source, cmd_shenv, opened_files):
     """Return the standard fds for cmd after applying redirects
 
@@ -720,6 +728,7 @@ def _executeShCmd(cmd, shenv, results, timeoutHelper):
         "pushd": executeBuiltinPushd,
         "rm": executeBuiltinRm,
         ":": executeBuiltinColon,
+        "unset": executeBuiltinUnset,
     }
     # To avoid deadlock, we use a single stderr stream for piped
     # output. This is null until we have seen some output using
diff --git a/llvm/utils/lit/tests/Inputs/shtest-unset/lit.cfg b/llvm/utils/lit/tests/Inputs/shtest-unset/lit.cfg
new file mode 100644
index 0000000000000..ec8c43263be72
--- /dev/null
+++ b/llvm/utils/lit/tests/Inputs/shtest-unset/lit.cfg
@@ -0,0 +1,10 @@
+import lit.formats
+
+config.name = "shtest-unset"
+config.suffixes = [".txt"]
+config.test_format = lit.formats.ShTest()
+config.test_source_root = None
+config.test_exec_root = None
+config.environment["FOO"] = "1"
+config.environment["BAR"] = "2"
+config.substitutions.append(("%{python}", '"%s"' % (sys.executable)))
diff --git a/llvm/utils/lit/tests/Inputs/shtest-unset/unset-multiple-variables.txt b/llvm/utils/lit/tests/Inputs/shtest-unset/unset-multiple-variables.txt
new file mode 100644
index 0000000000000..f7dc7e80bd93b
--- /dev/null
+++ b/llvm/utils/lit/tests/Inputs/shtest-unset/unset-multiple-variables.txt
@@ -0,0 +1,3 @@
+## Tests the 'unset' command with multiple variables.
+
+# RUN: unset FOO BAR
diff --git a/llvm/utils/lit/tests/Inputs/shtest-unset/unset-no-args.txt b/llvm/utils/lit/tests/Inputs/shtest-unset/unset-no-args.txt
new file mode 100644
index 0000000000000..bc9f27710c5bf
--- /dev/null
+++ b/llvm/utils/lit/tests/Inputs/shtest-unset/unset-no-args.txt
@@ -0,0 +1,3 @@
+## Tests the 'unset' command when no arguments are provided.
+
+# RUN: unset
diff --git a/llvm/utils/lit/tests/Inputs/shtest-unset/unset-nonexistent-variable.txt b/llvm/utils/lit/tests/Inputs/shtest-unset/unset-nonexistent-variable.txt
new file mode 100644
index 0000000000000..5fbe3fb757291
--- /dev/null
+++ b/llvm/utils/lit/tests/Inputs/shtest-unset/unset-nonexistent-variable.txt
@@ -0,0 +1,3 @@
+## Test the behavior of the 'unset' command when trying to unset a variable that does not exist.
+
+# RUN: unset NONEXISTENT
diff --git a/llvm/utils/lit/tests/Inputs/shtest-unset/unset-variable.txt b/llvm/utils/lit/tests/Inputs/shtest-unset/unset-variable.txt
new file mode 100644
index 0000000000000..11adcd234e717
--- /dev/null
+++ b/llvm/utils/lit/tests/Inputs/shtest-unset/unset-variable.txt
@@ -0,0 +1,3 @@
+## Tests the 'unset' command with a single variable
+
+# RUN: unset FOO
diff --git a/llvm/utils/lit/tests/shtest-unset.py b/llvm/utils/lit/tests/shtest-unset.py
new file mode 100644
index 0000000000000..6517864e8f9bd
--- /dev/null
+++ b/llvm/utils/lit/tests/shtest-unset.py
@@ -0,0 +1,42 @@
+## Check that the 'unset' command fails as expected for various tests.
+
+# RUN: not %{lit} -a -v %{inputs}/shtest-unset \
+# RUN: | FileCheck -match-full-lines %s
+#
+# END.
+
+## Check that the 'unset' command's expected failures.
+
+# CHECK: -- Testing: 4 tests{{.*}}
+
+# CHECK: FAIL: shtest-unset :: unset-multiple-variables.txt{{.*}}
+# CHECK: unset FOO BAR
+# CHECK-NEXT: # executed command: unset FOO BAR
+# CHECK-NEXT: # .---command stderr------------
+# CHECK-NEXT: # | 'unset' command is not supported by the lit internal shell. Please use 'env -u VARIABLE' to unset environment variables.
+# CHECK: # error: command failed with exit status: 127
+
+# CHECK: FAIL: shtest-unset :: unset-no-args.txt{{.*}}
+# CHECK: unset
+# CHECK-NEXT: # executed command: unset
+# CHECK-NEXT: # .---command stderr------------
+# CHECK-NEXT: # | 'unset' command is not supported by the lit internal shell. Please use 'env -u VARIABLE' to unset environment variables.
+# CHECK: # error: command failed with exit status: 127
+
+# CHECK: FAIL: shtest-unset :: unset-nonexistent-variable.txt{{.*}}
+# CHECK: unset NONEXISTENT
+# CHECK-NEXT: # executed command: unset NONEXISTENT
+# CHECK-NEXT: # .---command stderr------------
+# CHECK-NEXT: # | 'unset' command is not supported by the lit internal shell. Please use 'env -u VARIABLE' to unset environment variables.
+# CHECK: # error: command failed with exit status: 127
+
+# CHECK: FAIL: shtest-unset :: unset-variable.txt{{.*}}
+# CHECK: unset FOO
+# CHECK-NEXT: # executed command: unset FOO
+# CHECK-NEXT: # .---command stderr------------
+# CHECK-NEXT: # | 'unset' command is not supported by the lit internal shell. Please use 'env -u VARIABLE' to unset environment variables.
+# CHECK: # error: command failed with exit status: 127
+
+# CHECK: Total Discovered Tests: 4
+# CHECK: Failed: 4 {{\([0-9]*\.[0-9]*%\)}}
+# CHECK-NOT: {{.}}