Arthur 3: The War of the Two Worlds (French: Arthur 3: La Guerre des deux mondes) is a 2010 English-language French fantasy animated/live-action directed and co-written by Luc Besson, based on the fourth book of the Arthur children's books series by Besson. It is the sequel to Arthur and the Revenge of Maltazard (2009) and the third installment in the Arthur film series. The film was shot back-to-back with the previous installment.

Arthur 3: The War of the Two Worlds was released theatrically in France on 13 October 2010 by EuropaCorp. The film received mixed reviews from critics and was a box-office success in France. However, following its two predecessor's under-performance at the box-office internationally, the film generated huge losses for EuropaCorp. It was released as a direct-to-video in the United States by 20th Century Home Entertainment, while in the United Kingdom and Ireland, it was edited as one film with the second film under the title Arthur and the Great Adventure. The film marked Lou Reed's last acting role before his death in 2013.

It is the last installment in the main series. A spin-off, Arthur, malédiction, was released in France in 2022.