diff --git a/Data/Fin/List.hs b/Data/Fin/List.hs
--- a/Data/Fin/List.hs
+++ b/Data/Fin/List.hs
@@ -1,6 +1,14 @@
 module Data.Fin.List (Peano, List (..),
-                      fromList, uncons, head, tail, init, last, reverse, rotate, at, swap, (!!)) where
+                      fromList, uncons, head, tail, init, last, reverse, rotate, at, swap, (!!), findIndex) where
 
 import Prelude ()
-import Data.Fin.Private
-import Data.Peano
+import Data.Bool (Bool, bool)
+import Control.Applicative
+import Control.Category (id)
+import Data.Fin.Private as Fin
+import Data.Peano (Peano)
+
+findIndex :: Alternative p => (a -> Bool) -> List n a -> p (Fin n)
+findIndex p = \ case
+    Nil -> empty
+    a:.as -> bool id (pure Zero <|>) (p a) (Succ <$> findIndex p as)
diff --git a/Fin.cabal b/Fin.cabal
--- a/Fin.cabal
+++ b/Fin.cabal
@@ -1,5 +1,5 @@
 name:                Fin
-version:             0.2.8.0
+version:             0.2.9.0
 synopsis:            Finite totally-ordered sets
 -- description:         
 license:             BSD3