diff --git a/runtime/indent/wat.vim b/runtime/indent/wat.vim
new file mode 100644
index 0000000..08997f1
--- /dev/null
+++ b/runtime/indent/wat.vim
@@ -0,0 +1,17 @@
+" Vim indent file
+" Language:     WebAssembly
+" Maintainer:   rhysd <lin90162@yahoo.co.jp>
+" Last Change:  Nov 14, 2023
+" For bugs, patches and license go to https://github.com/rhysd/vim-wasm
+
+if exists("b:did_indent")
+    finish
+endif
+let b:did_indent = 1
+
+" WebAssembly text format is S-expression. We can reuse LISP indentation
+" logic.
+setlocal indentexpr=lispindent('.')
+setlocal noautoindent nosmartindent
+
+let b:undo_indent = "setl lisp< indentexpr<"