diff --git a/check-style.sh b/check-style.sh
index 2f88963..8ee6a00 100755
--- a/check-style.sh
+++ b/check-style.sh
@@ -41,57 +41,18 @@ case $1 in
         exit 2
 esac
 
-# Filter out symlinks from `affected_files`. We'll check the real files.
-# Use bash test operators instead of the 'file' command to avoid issues with
-# filenames containing special characters (colons, commas, etc).
-filtered_files=""
-for f in $affected_files; do
-    if [ ! -L "$f" ]; then
-        filtered_files="$filtered_files $f"
-    fi
-done
-affected_files=$(echo "$filtered_files" | xargs -r)
+# Source shared helper functions.
+dev_tools_path=$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" &>/dev/null && pwd)
+source "${dev_tools_path}/style-helpers.sh"
+
+# Filter out symlinks.
+filter_symlinks
 
 # Unset variable would be a sign of programmer error. We are not using '-e' in
 # this script as we'd like to handle these cases ourselves where relevant, i.e.,
 # allow more than one code check failure per run.
 set -u
 
-# Work from the git root. This is important to help some tools pick up the
-# correct configuration.
-git_root=$(git rev-parse --show-toplevel)
-cd "${git_root}"
-
-# Define a cummulative status code for the script. The value is Updated through
-# 'run_check' when running checks. A status code creater than 0 will indicate
-# that one or more checks failed.
-status_code=0
-
-# Run a code check command and update the cummulative error code.
-run_check() {
-    $@
-    status_code=$(($status_code + $?))
-}
-
-# Helper function to filter affected files by extension.
-get_files_by_extension() {
-    filter=""
-    for ext in $@; do
-        # We want a `.` to be a full stop, not a regexp wildcard.
-        filter="$(echo $ext | sed -e 's|^\.|\\.|')$|${filter}"
-    done
-    filter=$(echo $filter | sed -e 's/|$//')
-
-    echo $affected_files | tr ' ' '\n' | egrep $filter
-}
-
-# Helper function to get a checksum of a file list.
-# Calculates a per-file checksum, sorts by filename, and then returns a sum over
-# the sums.
-calculate_checksum() {
-    sha256sum $@ | sort -k 2 | sha256sum
-}
-
 # Check files that we can clang-format.
 clang_format_files=$(get_files_by_extension .cc .cpp .h .hpp .proto)
 if [ ! -z "${clang_format_files}" ]; then
@@ -106,7 +67,6 @@ if [ ! -z "${clang_format_files}" ]; then
     # invoke these scripts differently:
     # TODO: Consider tidying up this and perhaps solve the above ISSUE in the
     # process.
-    dev_tools_path=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
     case $mode in
         "full" )
             # For full checking, we can invoke the wrapper script directly.
diff --git a/fix-style.sh b/fix-style.sh
new file mode 100755
index 0000000..665ad20
--- /dev/null
+++ b/fix-style.sh
@@ -0,0 +1,74 @@
+#!/bin/bash
+# Fix formatting of files with unstaged changes in the git repo.
+
+
+# Source shared helper functions.
+dev_tools_path=$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" &>/dev/null && pwd)
+source "${dev_tools_path}/style-helpers.sh"
+
+# Get files with unstaged changes only (not staged; we assume that those have
+# already been formatted).
+affected_files=$(git diff --name-only 2>/dev/null)
+
+# If there's nothing to do, exit early.
+if [ -z "${affected_files}" ]; then
+    exit 0
+fi
+
+# Filter out symlinks.
+filter_symlinks
+
+# Filter to only files that actually exist (not deleted).
+existing_files=""
+for f in $affected_files; do
+    if [ -f "$f" ]; then
+        existing_files="$existing_files $f"
+    fi
+done
+affected_files=$(echo "$existing_files" | xargs -r)
+
+if [ -z "${affected_files}" ]; then
+    exit 0
+fi
+
+# Fix C/C++/proto files with clang-format.
+clang_format_files=$(get_files_by_extension .cc .cpp .h .hpp .proto)
+if [ ! -z "${clang_format_files}" ]; then
+    run_check clang-format -i ${clang_format_files}
+fi
+
+# Fix Bazel files with buildifier.
+bazel_files=$(get_files_by_extension .bzl .bazel BUILD WORKSPACE)
+if [ ! -z "${bazel_files}" ]; then
+    run_check buildifier --lint=fix --warnings=all ${bazel_files}
+fi
+
+# Fix Python files.
+python_files=$(get_files_by_extension .py)
+if [ ! -z "${python_files}" ]; then
+    run_check ruff check --fix ${python_files}
+    run_check isort ${python_files}
+    run_check yapf -i -p ${python_files}
+fi
+
+# Fix all files with prettier.
+run_check prettier --write --ignore-unknown \
+    --loglevel=warn ${affected_files}
+
+# Recurse into submodules that have unstaged changes. Only do this from the
+# top-level invocation (not from a recursive call inside a submodule) to avoid
+# infinite recursion.
+if [ -z "${_FIX_STYLE_RECURSING:-}" ]; then
+    export _FIX_STYLE_RECURSING=1
+    dirty_submodules=$(git submodule status --recursive \
+        2>/dev/null | grep '^+' | awk '{print $2}')
+    for submodule in $dirty_submodules; do
+        if [ -d "$submodule" ]; then
+            (cd "$submodule" && \
+                "${dev_tools_path}/fix-style.sh")
+            status_code=$(($status_code + $?))
+        fi
+    done
+fi
+
+exit $status_code
diff --git a/style-helpers.sh b/style-helpers.sh
new file mode 100755
index 0000000..22927bc
--- /dev/null
+++ b/style-helpers.sh
@@ -0,0 +1,47 @@
+#!/bin/bash
+# Shared helper functions for check-style.sh and fix-style.sh.
+
+# Work from the git root. This is important to help some tools pick
+# up the correct configuration.
+git_root=$(git rev-parse --show-toplevel)
+cd "${git_root}"
+
+# Define a cumulative status code. The value is updated through
+# `run_check` when running checks. A status code greater than 0
+# will indicate that one or more checks failed.
+status_code=0
+
+# Run a command and update the cumulative error code.
+run_check() {
+    "$@"
+    status_code=$(($status_code + $?))
+}
+
+# Filter `affected_files` by extension(s).
+get_files_by_extension() {
+    filter=""
+    for ext in "$@"; do
+        # We want a `.` to be a full stop, not a regexp wildcard.
+        filter="$(echo $ext | sed -e 's|^\.|\\.|')$|${filter}"
+    done
+    filter=$(echo $filter | sed -e 's/|$//')
+
+    echo $affected_files | tr ' ' '\n' | egrep $filter
+}
+
+# Get a checksum of a file list. Calculates a per-file checksum,
+# sorts by filename, and then returns a sum over the sums.
+calculate_checksum() {
+    sha256sum "$@" | sort -k 2 | sha256sum
+}
+
+# Filter out symlinks from `affected_files`.
+filter_symlinks() {
+    filtered_files=""
+    for f in $affected_files; do
+        if [ ! -L "$f" ]; then
+            filtered_files="$filtered_files $f"
+        fi
+    done
+    affected_files=$(echo "$filtered_files" | xargs -r)
+}