Little Wonder was a Double Fairlie type articulated locomotive designed by Robert Francis Fairlie. It was the first Double Fairlie locomotive on the Festiniog Railway and the fourth Double Fairlie locomotive to be built. It was an improvement on earlier designs because it had two fireboxes, instead of one, and this allowed it to steam more freely.
Little Wonder was hailed as a great success and attracted attention from around the world. However, various mechanical problems arose and the engine required frequent repairs. It was withdrawn from service in 1882.