The Ghost is a 1963 Italian horror film starring Barbara Steele. This is more gothic thriller than horror, and I thought it was a fine murder/revenge mystery story. You can't go wrong with Barbara Steele.
1000 Misspent Hours says, "anyone who enjoys Mario Bava’s moody, languorous gothics from the same era will find much to like about The Ghost." Weird Wild Realm says it's worth watching for Barbara Steele alone.