diff --git a/crates/uv-python/src/managed.rs b/crates/uv-python/src/managed.rs
index 6d715bd05..307eede29 100644
--- a/crates/uv-python/src/managed.rs
+++ b/crates/uv-python/src/managed.rs
@@ -1002,6 +1002,39 @@ pub fn create_link_to_executable(link: &Path, executable: &Path) -> Result<(), E
     }
 }
 
+/// Create or replace a link to a managed Python executable.
+///
+/// If a file already exists at the link path, it will be atomically replaced.
+///
+/// See [`create_link_to_executable`] for a variant that errors if the link already exists.
+pub fn replace_link_to_executable(link: &Path, executable: &Path) -> Result<(), Error> {
+    let link_parent = link.parent().ok_or(Error::NoExecutableDirectory)?;
+    fs_err::create_dir_all(link_parent).map_err(|err| Error::ExecutableDirectory {
+        to: link_parent.to_path_buf(),
+        err,
+    })?;
+
+    if cfg!(unix) {
+        replace_symlink(executable, link).map_err(|err| Error::LinkExecutable {
+            from: executable.to_path_buf(),
+            to: link.to_path_buf(),
+            err,
+        })
+    } else if cfg!(windows) {
+        use uv_trampoline_builder::windows_python_launcher;
+
+        let launcher = windows_python_launcher(executable, false)?;
+
+        uv_fs::write_atomic_sync(link, &*launcher).map_err(|err| Error::LinkExecutable {
+            from: executable.to_path_buf(),
+            to: link.to_path_buf(),
+            err,
+        })
+    } else {
+        unimplemented!("Only Windows and Unix are supported.")
+    }
+}
+
 // TODO(zanieb): Only used in tests now.
 /// Generate a platform portion of a key from the environment.
 pub fn platform_key_from_env() -> Result<String, Error> {
diff --git a/crates/uv-virtualenv/src/virtualenv.rs b/crates/uv-virtualenv/src/virtualenv.rs
index 18b356f35..68bec538e 100644
--- a/crates/uv-virtualenv/src/virtualenv.rs
+++ b/crates/uv-virtualenv/src/virtualenv.rs
@@ -16,7 +16,7 @@ use uv_fs::{CWD, Simplified, cachedir};
 use uv_platform_tags::Os;
 use uv_pypi_types::Scheme;
 use uv_python::managed::{
-    ManagedPythonInstallation, PythonMinorVersionLink, create_link_to_executable,
+    ManagedPythonInstallation, PythonMinorVersionLink, replace_link_to_executable,
 };
 use uv_python::{Interpreter, VirtualEnvironment};
 use uv_shell::escape_posix_for_single_quotes;
@@ -298,24 +298,24 @@ pub(crate) fn create(
     if cfg!(windows) {
         if using_minor_version_link {
             let target = scripts.join(WindowsExecutable::Python.exe(interpreter));
-            create_link_to_executable(target.as_path(), &executable_target)
+            replace_link_to_executable(target.as_path(), &executable_target)
                 .map_err(Error::Python)?;
             let targetw = scripts.join(WindowsExecutable::Pythonw.exe(interpreter));
-            create_link_to_executable(targetw.as_path(), &executable_target)
+            replace_link_to_executable(targetw.as_path(), &executable_target)
                 .map_err(Error::Python)?;
             if interpreter.gil_disabled() {
                 let targett = scripts.join(WindowsExecutable::PythonMajorMinort.exe(interpreter));
-                create_link_to_executable(targett.as_path(), &executable_target)
+                replace_link_to_executable(targett.as_path(), &executable_target)
                     .map_err(Error::Python)?;
                 let targetwt = scripts.join(WindowsExecutable::PythonwMajorMinort.exe(interpreter));
-                create_link_to_executable(targetwt.as_path(), &executable_target)
+                replace_link_to_executable(targetwt.as_path(), &executable_target)
                     .map_err(Error::Python)?;
             }
         } else if matches!(interpreter.platform().os(), Os::Pyodide { .. }) {
             // For Pyodide, link only `python.exe`.
             // This should not be copied as `python.exe` is a wrapper that launches Pyodide.
             let target = scripts.join(WindowsExecutable::Python.exe(interpreter));
-            create_link_to_executable(target.as_path(), &executable_target)
+            replace_link_to_executable(target.as_path(), &executable_target)
                 .map_err(Error::Python)?;
         } else {
             // Always copy `python.exe`.
diff --git a/crates/uv/tests/it/python_install.rs b/crates/uv/tests/it/python_install.rs
index 94d5ba78e..275befb98 100644
--- a/crates/uv/tests/it/python_install.rs
+++ b/crates/uv/tests/it/python_install.rs
@@ -2913,6 +2913,58 @@ fn python_install_emulated_windows_x86_on_x64() {
     ");
 }
 
+// Creating a venv with `--allow-existing` over an existing managed venv should succeed.
+//
+// Regression test for <https://github.com/astral-sh/uv/issues/17963>.
+#[test]
+fn install_managed_venv_allow_existing() {
+    let context = uv_test::test_context_with_versions!(&[])
+        .with_filtered_python_keys()
+        .with_filtered_exe_suffix()
+        .with_filtered_latest_python_versions()
+        .with_managed_python_dirs()
+        .with_python_download_cache()
+        .with_filtered_python_install_bin();
+
+    // Install a managed Python version.
+    uv_snapshot!(context.filters(), context.python_install().arg("3.13"), @"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Installed Python 3.13.[LATEST] in [TIME]
+     + cpython-3.13.[LATEST]-[PLATFORM] (python3.13)
+    ");
+
+    // Create a virtual environment using the managed installation.
+    uv_snapshot!(context.filters(), context.venv().arg("-p").arg("3.13")
+        .arg(context.venv.as_os_str()), @"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Using CPython 3.13.[LATEST]
+    Creating virtual environment at: .venv
+    Activate with: source .venv/[BIN]/activate
+    ");
+
+    // Create the venv again with `--allow-existing` — this should not fail.
+    uv_snapshot!(context.filters(), context.venv().arg("-p").arg("3.13")
+        .arg("--allow-existing")
+        .arg(context.venv.as_os_str()), @"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Using CPython 3.13.[LATEST]
+    Creating virtual environment at: .venv
+    Activate with: source .venv/[BIN]/activate
+    ");
+}
+
 // A virtual environment should track the latest patch version installed.
 #[test]
 fn install_transparent_patch_upgrade_uv_venv() {