Ferdinard Munier holds the claim of first to play Santa in the movies with his roles in “Babes in Toyland” (1934) and “Road to Utopia” (1946). However, these were minor supporting parts.
The first actor to play Santa Claus as a featured character in a film falls to Edmund Gwenn in the 1947 film “Miracle on 34th Street.” And he is the only actor to receive an Academy Award for playing the role. http://en.wikipedia.org/wiki/List_of_actors_who_played_Santa_Claus
Gwenn was born Edmund Kellaway in Wandsworth, London, on September 26, 1877. Gwenn was an accomplished actor before “Miracle”. The studio first offered the role of Kris Kringle to Gwenn’s cousin, the well-known character actor 'Cecil Kellaway', but he had turned it down. The studio then offered it to Gwenn, who pounced on it. His performance was to earn him an Academy Award as Best Supporting Actor (at age 71).
Gwenn took the role seriously. Though rotund, he didn't feel he was round enough to look like the jolly old elf most people expected after having read Clement Moore's "The Night before Christmas". He could have chosen to wear padding, but he resisted that as too artificial. So Gwenn put on almost 30 pounds for the role. http://www.imdb.com/name/nm0350324/bio?ref_=nm_ov_bio_sm
Gwenn, dressed in his role as Santa: http://cornucopia.theiapolis.com/goodies/5606n/edmund-gwenn.html