X+Y, released in the US as A Brilliant Young Mind, is a 2014 British drama film directed by Morgan Matthews and starring Asa Butterfield, Rafe Spall and Sally Hawkins.

The film, inspired by the 2007 documentary Beautiful Young Minds, focuses on a teenage English mathematics prodigy named Nathan (Asa Butterfield) who has difficulty understanding people, and is autistic, but finds comfort in numbers. When he is chosen to represent the United Kingdom at the International Mathematical Olympiad (IMO), Nathan embarks on a journey in which he faces unexpected challenges, such as understanding the nature of love. The character of Nathan was based on Daniel Lightwing who won a silver medal at the 2006 IMO.

The film premiered at the Toronto International Film Festival on 5 September 2014. The European premiere was at the BFI London Film Festival on 13 October 2014, and the UK cinema release was on 13 March 2015.