diff --git a/nat-optics.cabal b/nat-optics.cabal
--- a/nat-optics.cabal
+++ b/nat-optics.cabal
@@ -1,7 +1,7 @@
 cabal-version: 3.0
 
 name: nat-optics
-version: 1.0.0.3
+version: 1.0.0.4
 category: Numeric, Optics
 
 synopsis:
diff --git a/src/NatOptics/Signed.hs b/src/NatOptics/Signed.hs
--- a/src/NatOptics/Signed.hs
+++ b/src/NatOptics/Signed.hs
@@ -4,14 +4,16 @@
   (
     Signed (..),
     intIso,
+    intNatIso,
   )
   where
 
 import Data.Eq            ( Eq )
 import Data.Ord           ( Ord, compare, Ordering (..) )
-import Text.Show          ( Show )
+import Numeric.Natural    ( Natural )
 import Optics.Core        ( Iso', iso )
-import Prelude            ( Integer, abs, negate )
+import Prelude            ( Integer, abs, negate, fromIntegral )
+import Text.Show          ( Show )
 
 import NatOptics.Positive.Unsafe ( Positive (..) )
 
@@ -29,3 +31,15 @@
         Zero -> 0
         Plus (PositiveUnsafe x) -> x
         Minus (PositiveUnsafe x) -> negate x
+
+intNatIso :: Iso' Integer (Signed Natural)
+intNatIso = iso f g
+  where
+    f x = case compare x 0 of
+        EQ -> Zero
+        LT -> Minus (PositiveUnsafe (fromIntegral (abs x)))
+        GT -> Plus (PositiveUnsafe (fromIntegral x))
+    g y = case y of
+        Zero -> 0
+        Plus (PositiveUnsafe x) -> fromIntegral x
+        Minus (PositiveUnsafe x) -> negate (fromIntegral x)
diff --git a/test/Main.hs b/test/Main.hs
--- a/test/Main.hs
+++ b/test/Main.hs
@@ -60,6 +60,15 @@
             specify "0" $ review S.intIso S.Zero `shouldBe` 0
             specify "3" $ review S.intIso (S.Plus (Pos.PositiveUnsafe 3)) `shouldBe` 3
             specify "-5" $ review S.intIso (S.Minus (Pos.PositiveUnsafe 5)) `shouldBe` (-5)
+    describe "intNatIso" $ do
+        describe "view" $ do
+            specify "0" $ view S.intNatIso 0 `shouldBe` S.Zero
+            specify "3" $ view S.intNatIso 3 `shouldBe` S.Plus (Pos.PositiveUnsafe 3)
+            specify "-5" $ view S.intNatIso (-5) `shouldBe` S.Minus (Pos.PositiveUnsafe 5)
+        describe "review" $ do
+            specify "0" $ review S.intNatIso S.Zero `shouldBe` 0
+            specify "3" $ review S.intNatIso (S.Plus (Pos.PositiveUnsafe 3)) `shouldBe` 3
+            specify "-5" $ review S.intNatIso (S.Minus (Pos.PositiveUnsafe 5)) `shouldBe` (-5)
 
 mathSpec :: SpecWith ()
 mathSpec = describe "Positive math" $ do