Thomas & Friends: The Adventure Begins is a 2015 British animated adventure comedy film and the eighth feature-length special based on the British television series Thomas & Friends. The film was produced and distributed by HIT Entertainment with animation production by Canadian-based Arc Productions. The film functions as a prequel to the show, and a retelling of the first two books of The Railway Series; The Three Railway Engines and Thomas the Tank Engine, as well as the first seven episodes of the first series. It was made to commemorate the 70th anniversary of The Railway Series, and was the first installment to officially adapt a story from The Railway Series since series 4. The film also saw John Hasler and Joseph May take over the voice role of Thomas the Tank Engine in the United Kingdom and the United States respectively.

The film was first released direct-to-video on DVD in the United States on 3 March 2015 and in the United Kingdom on 27 July.