"Therefore I Am" is a song by American singer-songwriter Billie Eilish and the second single from her second studio album, Happier Than Ever (2021). It was released on November 12, 2020, through Darkroom and Interscope Records. It is an uptempo, hip hop-influenced pop, dark pop, R&B, and electropop track. Eilish wrote the song with its producer, Finneas O'Connell.

The song received positive reviews from music critics, with many of them comparing it to Eilish's hit single "Bad Guy". "Therefore I Am" was featured in 2020 year-end lists by multiple publications, including Billboard, NME, and Uproxx. The song peaked at number two on the US Billboard Hot 100, giving Eilish her fourth top-10 hit in the United States. The song further reached the top five on the Billboard airplay Hot Rock & Alternative Songs charts and number one on the Mainstream Top 40 chart. It peaked at number one on the singles charts in Greece, Ireland, Lithuania, and New Zealand, alongside receiving a platinum certification in Canada from Music Canada (MC).

Released on the same day as its single, the song's music video was filmed inside the Glendale Galleria shopping mall in Glendale, California. Due to the COVID-19 pandemic, the mall had been closed to the public, hence the absence of people in the mall throughout the music video. Self-directed by Eilish, the music video features her alone in an empty shopping mall, stealing and eating various consumables from food stalls in the mall. Eilish performed the song at American Music Awards of 2020 in November 2020 and as part of a concert film and a world tour in support of Happier Than Ever.