diff --git a/prim-array.cabal b/prim-array.cabal
--- a/prim-array.cabal
+++ b/prim-array.cabal
@@ -1,5 +1,5 @@
 name: prim-array
-version: 0.2.1
+version: 0.2.2
 synopsis: Primitive byte array with type variable
 homepage: https://github.com/andrewthad/prim-array#readme
 license: BSD3
@@ -21,6 +21,7 @@
       base >= 4.9 && < 5
     , primitive >= 0.6 && < 0.7
     , ghc-prim >= 0.5 && < 0.6
+    , semigroups
   default-language: Haskell2010
 
 source-repository head
diff --git a/src/Data/Primitive/PrimArray.hs b/src/Data/Primitive/PrimArray.hs
--- a/src/Data/Primitive/PrimArray.hs
+++ b/src/Data/Primitive/PrimArray.hs
@@ -42,6 +42,8 @@
 import Data.Primitive
 import Control.Monad.Primitive
 import Control.Monad.ST
+import Data.Semigroup (Semigroup(..))
+import qualified Data.Semigroup as SG
 import qualified Data.List as L
 import qualified Data.Primitive.Types as PT
 
@@ -88,19 +90,24 @@
     then indexPrimArray arr ix : go (ix + 1)
     else []
 
+appendPrimArray :: Prim a => PrimArray a -> PrimArray a -> PrimArray a 
+appendPrimArray a b = runST $ do
+  let szA = sizeofPrimArray a
+  let szB = sizeofPrimArray b
+  c <- newPrimArray (szA + szB)
+  copyPrimArray c 0 a 0 szA
+  copyPrimArray c szA b 0 szB
+  unsafeFreezePrimArray c
 
+instance Prim a => Semigroup (PrimArray a) where
+  (<>) = appendPrimArray
+
 -- It is actually possible to write this without the Prim constraint
 -- on the type variable a. You just copy the byte arrays using
 -- more primitive operations.
 instance Prim a => Monoid (PrimArray a) where
   mempty = emptyPrimArray
-  mappend a b = runST $ do
-    let szA = sizeofPrimArray a
-    let szB = sizeofPrimArray b
-    c <- newPrimArray (szA + szB)
-    copyPrimArray c 0 a 0 szA
-    copyPrimArray c szA b 0 szB
-    unsafeFreezePrimArray c
+  mappend = (SG.<>)
 
 emptyPrimArray :: PrimArray a
 {-# NOINLINE emptyPrimArray #-}