diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Revision history for unlifted
 
+## 0.2.3.0 -- 2025-04-07
+
+* Add `IO#` and `MaybeWord16#`.
+
 ## 0.2.2.0 -- 2024-02-07
 
 * Export `Text#` in `Data.Unlifted`.
diff --git a/src/Control/Monad/IO/Unlifted.hs b/src/Control/Monad/IO/Unlifted.hs
new file mode 100644
--- /dev/null
+++ b/src/Control/Monad/IO/Unlifted.hs
@@ -0,0 +1,16 @@
+{-# language MagicHash #-}
+
+module Control.Monad.IO.Unlifted
+  ( IO#(..)
+  , lift
+  , unlift
+  ) where
+
+import GHC.IO (IO(IO))
+import Data.Unlifted (IO#(..))
+
+lift :: IO# a -> IO a
+lift (IO# f) = IO f
+
+unlift :: IO a -> IO# a
+unlift (IO f) = IO# f
diff --git a/src/Data/Maybe/Word16.hs b/src/Data/Maybe/Word16.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Maybe/Word16.hs
@@ -0,0 +1,35 @@
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE GADTSyntax #-}
+{-# LANGUAGE KindSignatures #-}
+{-# LANGUAGE MagicHash #-}
+{-# LANGUAGE PatternSynonyms #-}
+{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE UnboxedTuples #-}
+{-# LANGUAGE UnliftedNewtypes #-}
+{-# LANGUAGE ViewPatterns #-}
+
+module Data.Maybe.Word16
+  ( MaybeWord16# (..)
+  , pattern JustWord16#
+  , pattern NothingWord16#
+  ) where
+
+import GHC.Exts
+
+-- The value 65536 is used to mean Nothing. Values above this
+-- should not be used.
+newtype MaybeWord16# :: TYPE 'WordRep where
+  MaybeWord16# :: Word# -> MaybeWord16#
+
+pattern JustWord16# :: Word16# -> MaybeWord16#
+pattern JustWord16# a <- (helper -> (# 0#, a #))
+  where
+    JustWord16# w = MaybeWord16# (word16ToWord# w)
+
+helper :: MaybeWord16# -> (# Int#, Word16# #)
+{-# INLINE helper #-}
+helper (MaybeWord16# x) = (# eqWord# x 65536##, wordToWord16# x #)
+
+pattern NothingWord16# :: MaybeWord16#
+pattern NothingWord16# = MaybeWord16# 65536##
diff --git a/src/Data/Text/Short/Unlifted.hs b/src/Data/Text/Short/Unlifted.hs
--- a/src/Data/Text/Short/Unlifted.hs
+++ b/src/Data/Text/Short/Unlifted.hs
@@ -1,20 +1,39 @@
 {-# LANGUAGE GADTSyntax #-}
+{-# LANGUAGE PatternSynonyms #-}
+{-# LANGUAGE ViewPatterns #-}
+{-# LANGUAGE UnboxedTuples #-}
 {-# LANGUAGE KindSignatures #-}
 {-# LANGUAGE MagicHash #-}
 {-# LANGUAGE UnliftedNewtypes #-}
 
 module Data.Text.Short.Unlifted
   ( ShortText# (..)
+  , pattern Empty#
   , lift
   , unlift
   ) where
 
+import GHC.Exts (Int#)
 import Data.ByteString.Short.Internal as TS
 import Data.Text.Short (ShortText)
 import Data.Unlifted (ShortText# (ShortText#))
+import GHC.Exts ((==#))
 
 import qualified Data.Text.Short as TS
 import qualified Data.Text.Short.Unsafe as TS
+import qualified GHC.Exts as Exts
+
+pattern Empty# :: ShortText#
+pattern Empty# <- (null# -> 1#)
+  where
+  Empty# = empty# (# #)
+
+empty# :: (# #) -> ShortText#
+empty# _ =
+  ShortText# (Exts.runRW# (\s0 -> case Exts.newByteArray# 0# s0 of { (# s1, b #) -> case Exts.unsafeFreezeByteArray# b s1 of { (# _, y #) -> y}}))
+
+null# :: ShortText# -> Int#
+null# (ShortText# x) = Exts.sizeofByteArray# x ==# 0#
 
 lift :: ShortText# -> ShortText
 lift (ShortText# x) = TS.fromShortByteStringUnsafe (SBS x)
diff --git a/src/Data/Unlifted.hs b/src/Data/Unlifted.hs
--- a/src/Data/Unlifted.hs
+++ b/src/Data/Unlifted.hs
@@ -13,6 +13,7 @@
     Maybe# (..)
   , Either# (..)
   , ST# (..)
+  , IO# (..)
 
     -- * Text
   , ShortText# (..)
@@ -29,6 +30,7 @@
   ) where
 
 import Data.Kind (Type)
+import GHC.Exts (RealWorld)
 import GHC.Exts (ByteArray#, Int32#, Levity (Unlifted), MutableByteArray#, RuntimeRep (..), State#, TYPE, Word#)
 
 {- | Variant of @ST@ where the argument type does not have to be lifted.
@@ -40,6 +42,13 @@
     { unST# :: State# s -> (# State# s, a #)
     } ->
     ST# s a
+
+newtype IO# :: forall (r :: RuntimeRep). TYPE r -> Type where
+  IO# ::
+    forall (r :: RuntimeRep) (a :: TYPE r).
+    { unIO# :: State# RealWorld -> (# State# RealWorld, a #)
+    } ->
+    IO# a
 
 -- | Unboxed variant of @Bool@.
 newtype Bool# :: TYPE 'WordRep where
diff --git a/unlifted.cabal b/unlifted.cabal
--- a/unlifted.cabal
+++ b/unlifted.cabal
@@ -1,6 +1,6 @@
 cabal-version:   2.4
 name:            unlifted
-version:         0.2.2.0
+version:         0.2.3.0
 synopsis:        Unlifted and levity-polymorphic types
 description:
   Unlifted and levity-polymorphic variants of several types from
@@ -29,8 +29,10 @@
   exposed-modules:
     Data.Either.Void
     Data.Maybe.Void
+    Data.Maybe.Word16
     Data.Text.Short.Unlifted
     Data.Unlifted
+    Control.Monad.IO.Unlifted
 
   hs-source-dirs:  src
   build-depends: