It's Such a Beautiful Day is a 2012 American experimental adult animated comedy-drama film directed, written, animated, photographed, produced and narrated by Don Hertzfeldt.

The film tells the story of a character named Bill, who struggles with memory loss and surreal visions, among other symptoms of an unknown neurological problem. The film employs both offbeat humor and serious philosophical musings. The film mostly consists of stick figures, with stylized footage from the real world appearing in many "split screen" windows, photographed through multiple exposures. Hertzfeldt serves as the film's uncredited narrator.

The film is divided into three chapters, all of which were originally released in theaters as animated short films. The first part, Everything Will Be OK, was released in 2006 and received the Grand Prize at the Sundance Film Festival. The second short, I Am So Proud of You, was released in 2008, and the titular third film, It's Such a Beautiful Day, was released in 2011. The three short films received over 90 film festival awards upon their original releases. In 2012, the three chapters were combined and released as a new feature film.

The film received widespread critical acclaim, with its experimental storytelling and surrealistic elements in animation being singled out for praise. Many critics listed the feature film release as one of the best films of 2012. Since then, It's Such a Beautiful Day has been widely regarded by critics as one of the best animated films of all time.