"Roar" is a song by American singer Katy Perry for her fourth studio album, Prism. It was released as the lead single from the record on August 10, 2013. Perry co-wrote the song with Bonnie McKee and its producers Dr. Luke, Max Martin, and Cirkut. It is a pop song containing elements of arena rock and lyrics centering on standing up for oneself and self-empowerment.

To promote the song, Perry performed under the Brooklyn Bridge at the end of the 2013 MTV Video Music Awards, on The X Factor Australia, at the Sydney Opera House in late October 2013, and on the German TV show Schlag den Raab. Grady Hall and Mark Kudsi directed the song's music video, which features Perry trying to adapt to the jungle and taming a tiger after surviving a plane crash. Though the song received generally mixed reviews, it was nominated for Song of the Year and Best Pop Solo Performance at the 56th Annual Grammy Awards.

The song was a commercial success, topping charts in Australia, Austria, Canada, Ireland, Israel, Lebanon, New Zealand, Scotland, Slovenia, South Korea, the United Kingdom, and the United States. By the end of 2013, "Roar" had sold over 9.9 million units globally according to the International Federation of the Phonographic Industry. "Roar" has sold 6.6 million copies in the US, over 1 million in the United Kingdom, and was Australia's best-selling female song of the year with 560,000 copies sold within that time. When "Roar" was certified Diamond by the Recording Industry Association of America, Perry became the first artist to have three Diamond certified singles in the country, the other being "Firework" and "Dark Horse". In February 2020, the music video for "Roar" reached 3 billion views, becoming the first female-centered video to reach the milestone in YouTube's history.