diff --git a/.config/nvim/plugin/auto-prune.lua b/.config/nvim/plugin/auto-prune.lua
new file mode 100644
--- /dev/null
+++ b/.config/nvim/plugin/auto-prune.lua
@@ -0,0 +1,28 @@
+-- Prune old swap, backup, and undo files at startup
+
+local fn, fs = vim.fn, vim.fs
+
+local function prune_files(path, days)
+  local sunset = os.time() - (days * 86400)
+  path = fs.normalize(path)
+
+  if fn.getftype(path) == "" then return end
+
+  for fname, type in fs.dir(path) do
+    local fpath = fs.normalize(path .. "/" .. fname)
+    if type == "file" and fn.getftime(fpath) < sunset then
+      os.remove(fpath)
+    end
+  end
+end
+
+vim.api.nvim_create_autocmd("VimEnter", {
+  pattern = "*",
+  group = vim.api.nvim_create_augroup("AutoPrune", { clear = true }),
+  callback = function()
+    if vim.v.vim_did_enter then return end
+    if vim.go.swapfile then prune_files(vim.go.directory, 90) end
+    if vim.go.backup then prune_files(vim.go.backupdir, 90) end
+    if vim.go.undofile then prune_files(vim.go.undodir, 90) end
+  end
+})