"Stronger (What Doesn't Kill You)", also known as "What Doesn't Kill You (Stronger)", is a song by American pop rock singer Kelly Clarkson. It was written by Ali Tamposi, David Gamson, Greg Kurstin and produced by Kurstin. It will be sent to mainstream radio on January 17, 2012, by RCA, as the second single from Clarkson's fifth album, Stronger. The song is an uptempo pop rock song that uses vibrant beat pulsating with synth and electric guitar. According to Clarkson, the song was inspired by Friedrich Nietzsche quote, "That which does not kill us makes us stronger," and its lyrics contain the theme of empowerment. The song is considered as an anthem for recovery after the end of a bad relationship.
The song received generally positive reviews from music critics, who praised Clarkson's vocal performance, some of whom highlighted it as one of the album's musical highlights. Immediately following the release of Stronger, the song entered the Billboard Hot 100 and Canadian Hot 100 at number 64. Internationally, the song received moderate success, peaking at number 21 in Australia, and number 26 in New Zealand.
The song's accompanying music video was directed by Shane Drake. It incorporates the theme of global flash mob which features worldwide fan involvement. The music video garnered positive receptions from critics who felt that its overall impact was joyful and fun. Clarkson has performed "Stronger (What Doesn't Kill You)" in several live appearances, notably during the U.S. X Factor result show and the VH1 Divas 2011.