diff --git a/XMonad/Actions/ToggleFullFloat.hs b/XMonad/Actions/ToggleFullFloat.hs
new file mode 100644
index 0000000000..0f176b5206
--- /dev/null
+++ b/XMonad/Actions/ToggleFullFloat.hs
@@ -0,0 +1,122 @@
+-- |
+-- Module      :  XMonad.Actions.ToggleFullFloat
+-- Description :  Fullscreen (float) a window while remembering its original state.
+-- Copyright   :  (c) 2022 Tomáš Janoušek <tomi@nomi.cz>
+-- License     :  BSD3
+-- Maintainer  :  Tomáš Janoušek <tomi@nomi.cz>
+--
+module XMonad.Actions.ToggleFullFloat (
+    -- * Usage
+    -- $usage
+    toggleFullFloatEwmhFullscreen,
+    toggleFullFloat,
+    fullFloat,
+    unFullFloat,
+    gcToggleFullFloat,
+    ) where
+
+import qualified Data.Map.Strict as M
+
+import XMonad
+import XMonad.Prelude
+import XMonad.Hooks.EwmhDesktops (setEwmhFullscreenHooks)
+import XMonad.Hooks.ManageHelpers
+import qualified XMonad.StackSet as W
+import qualified XMonad.Util.ExtensibleState as XS
+
+-- ---------------------------------------------------------------------
+-- $usage
+--
+-- The main use-case is to make 'ewmhFullscreen' (re)store the size and
+-- position of floating windows instead of just unconditionally sinking them
+-- into the floating layer. To enable this, you'll need this in your
+-- @xmonad.hs@:
+--
+-- > import XMonad
+-- > import XMonad.Actions.ToggleFullFloat
+-- > import XMonad.Hooks.EwmhDesktops
+-- >
+-- > main = xmonad $ … . toggleFullFloatEwmhFullscreen . ewmhFullscreen . ewmh . … $ def{…}
+--
+-- Additionally, this "smart" fullscreening can be bound to a key and invoked
+-- manually whenever one needs a larger window temporarily:
+--
+-- >   , ((modMask .|. shiftMask, xK_t), withFocused toggleFullFloat)
+
+newtype ToggleFullFloat = ToggleFullFloat{ fromToggleFullFloat :: M.Map Window (Maybe W.RationalRect) }
+    deriving (Show, Read)
+
+instance ExtensionClass ToggleFullFloat where
+    extensionType = PersistentExtension
+    initialValue = ToggleFullFloat mempty
+
+-- | Full-float a window, remembering its state (tiled/floating and
+-- position/size).
+fullFloat :: Window -> X ()
+fullFloat = windows . appEndo <=< runQuery doFullFloatSave
+
+-- | Restore window to its remembered state.
+unFullFloat :: Window -> X ()
+unFullFloat = windows . appEndo <=< runQuery doFullFloatRestore
+
+-- | Full-float a window, if it's not already full-floating. Otherwise,
+-- restore its original state.
+toggleFullFloat :: Window -> X ()
+toggleFullFloat w = ifM (isFullFloat w) (unFullFloat w) (fullFloat w)
+
+isFullFloat :: Window -> X Bool
+isFullFloat w = gets $ (Just fullRect ==) . M.lookup w . W.floating . windowset
+  where
+    fullRect = W.RationalRect 0 0 1 1
+
+doFullFloatSave :: ManageHook
+doFullFloatSave = do
+    w <- ask
+    liftX $ do
+        f <- gets $ M.lookup w . W.floating . windowset
+        -- @M.insertWith const@ = don't overwrite stored original state
+        XS.modify' $ ToggleFullFloat . M.insertWith const w f . fromToggleFullFloat
+    doFullFloat
+
+doFullFloatRestore :: ManageHook
+doFullFloatRestore = do
+    w <- ask
+    mf <- liftX $ do
+        mf <- XS.gets $ M.lookup w . fromToggleFullFloat
+        XS.modify' $ ToggleFullFloat . M.delete w . fromToggleFullFloat
+        pure mf
+    doF $ case mf of
+        Just (Just f) -> W.float w f  -- was floating before
+        Just Nothing -> W.sink w      -- was tiled before
+        Nothing -> W.sink w           -- fallback when not found in ToggleFullFloat
+
+-- | Install ToggleFullFloat garbage collection hooks.
+--
+-- Note: This is included in 'toggleFullFloatEwmhFullscreen', only needed if
+-- using the 'toggleFullFloat' separately from the EWMH hook.
+gcToggleFullFloat :: XConfig a -> XConfig a
+gcToggleFullFloat c = c { startupHook     = startupHook c <> gcToggleFullFloatStartupHook
+                        , handleEventHook = handleEventHook c <> gcToggleFullFloatEventHook }
+
+-- | ToggleFullFloat garbage collection: drop windows when they're destroyed.
+gcToggleFullFloatEventHook :: Event -> X All
+gcToggleFullFloatEventHook DestroyWindowEvent{ev_window = w} = do
+    XS.modify' $ ToggleFullFloat . M.delete w . fromToggleFullFloat
+    mempty
+gcToggleFullFloatEventHook _ = mempty
+
+-- | ToggleFullFloat garbage collection: restrict to existing windows at
+-- startup.
+gcToggleFullFloatStartupHook :: X ()
+gcToggleFullFloatStartupHook = withWindowSet $ \ws ->
+    XS.modify' $ ToggleFullFloat . M.filterWithKey (\w _ -> w `W.member` ws) . fromToggleFullFloat
+
+-- | Hook this module into 'XMonad.Hooks.EwmhDesktops.ewmhFullscreen'. This
+-- makes windows restore their original state (size and position if floating)
+-- instead of unconditionally sinking into the tiling layer.
+--
+-- ('gcToggleFullFloat' is included here.)
+toggleFullFloatEwmhFullscreen :: XConfig a -> XConfig a
+toggleFullFloatEwmhFullscreen =
+    setEwmhFullscreenHooks doFullFloatSave doFullFloatRestore .
+    gcToggleFullFloat
diff --git a/XMonad/Hooks/EwmhDesktops.hs b/XMonad/Hooks/EwmhDesktops.hs
index c4161aa8f3..84cd7afbe8 100644
--- a/XMonad/Hooks/EwmhDesktops.hs
+++ b/XMonad/Hooks/EwmhDesktops.hs
@@ -250,6 +250,9 @@ setEwmhActivateHook h = XC.modifyDef $ \c -> c{ activateHook = h }
 -- stateless: windows are fullscreened by turning them into fullscreen floats,
 -- and reverted by sinking them into the tiling layer. This behaviour can be
 -- configured by supplying a pair of 'ManageHook's to 'setEwmhFullscreenHooks'.
+--
+-- See "XMonad.Actions.ToggleFullFloat" for a pair of hooks that store the
+-- original state of floating windows.
 
 -- | Set (replace) the hooks invoked when clients ask to add/remove the
 -- $_NET_WM_STATE_FULLSCREEN@ state. The defaults are 'doFullFloat' and
diff --git a/xmonad-contrib.cabal b/xmonad-contrib.cabal
index 942e48b7a2..72a9b6da07 100644
--- a/xmonad-contrib.cabal
+++ b/xmonad-contrib.cabal
@@ -147,6 +147,7 @@ library
                         XMonad.Actions.SwapWorkspaces
                         XMonad.Actions.TagWindows
                         XMonad.Actions.TiledWindowDragging
+                        XMonad.Actions.ToggleFullFloat
                         XMonad.Actions.TopicSpace
                         XMonad.Actions.TreeSelect
                         XMonad.Actions.UpdateFocus