Philip Seymour Hoffman and Toni Collette voice the lead characters, a lonely Australian girl and a middle-aged New Yorker with Asperger's Syndrome who become pen pals.
The story is based on Elliot's personal experiences as a pen-pal lasting more than 20 years. Barry Humphries narrates the tale, which is produced by Melanie Coombs and features a cameo from Eric Bana.
Mary And Max marks Elliot's feature directorial debut. He won the animated short film Oscar in 2004 for Harvie Krumpet, which screened at Sundance that year and was produced by Coombs. Elliot has won Australian Film Institute animated short film awards for Harvie Krumpet, Uncle, Cousin and Brother.
'This portrait of a global friendship between two marvellously dysfunctional people is an exceptionally moving, funny and thought-provoking work,' Sundance Film Festival director Geoffrey Gilmore said.
'Mary And Max is the first film of its kind to open the festival and we anticipate audiences will embrace Adam Elliot's feature-length directorial debut for its poignant story, exceptional voice talent and technological creativity.'
'By Opening Night it will have been five years since Melanie and I began working on the film,' Elliot said. 'It has been a whale of a pregnancy and we are so thrilled that the birth will be in Sundance. It is a dream come true to unveil our film in such an honored and nourishing environment.'
Icon holds worldwide rights and Icon's Mark Gooder served as executive producer with Paul Hardart, Tom Hardart, Bryce Menzies and Jonathan Page. Screen Australia, Adirondack Pictures and Film Victoria financed the project.
The festival is scheduled to run from January 15-25. The entire programme will be announced on December 3 and 4.