The Man Who Knew Infinity is a 2015 British biographical drama film about the Indian mathematician Srinivasa Ramanujan, based on the 1991 book of the same name by Robert Kanigel.

The film stars Dev Patel as Srinivasa Ramanujan, a real-life mathematician who, after growing up poor in Madras, India, earns admittance to Cambridge University during World War I, where he becomes a pioneer in mathematical theories with the guidance of his professor, G. H. Hardy, portrayed by Jeremy Irons.

Filming began in August 2014 at Trinity College, Cambridge after eight years in development. The film had its world premiere as a gala presentation at the 2015 Toronto International Film Festival, and was selected as the opening gala of the 2015 Zurich Film Festival. It also played other film festivals including Singapore International Film Festival and Dubai International Film Festival.