diff --git a/lua/autocmd.lua b/lua/autocmd.lua
index fd250a4..e3afaf9 100644
--- a/lua/autocmd.lua
+++ b/lua/autocmd.lua
@@ -54,4 +54,33 @@ vim.api.nvim_create_user_command('WordCount', function()
   print('Word count: ' .. words)
 end, { desc = 'Count words in current buffer' })
 
+vim.api.nvim_create_user_command('HeaderGuard', function()
+  local filename = vim.fn.expand '%:t' -- filename.ext
+  local stem = vim.fn.expand '%:t:r' -- filename without extension
+  local ext = vim.fn.expand '%:e' -- file extension
+
+  if ext ~= 'h' then
+    print 'HeaderGuard: Not a .h file!'
+    return
+  end
+
+  local guard = string.upper(stem) .. '_H'
+
+  -- Insert at top
+  vim.api.nvim_buf_set_lines(0, 0, 0, false, {
+    '#ifndef ' .. guard,
+    '#define ' .. guard,
+    '',
+  })
+
+  -- Insert at bottom
+  local last_line = vim.api.nvim_buf_line_count(0)
+  vim.api.nvim_buf_set_lines(0, last_line, last_line, false, {
+    '',
+    '#endif // ' .. guard,
+  })
+
+  print('Header guard inserted: ' .. guard)
+end, { desc = 'Insert header guard for current .h file' })
+
 -- vim: ts=2 sts=2 sw=2 et