"Cruel Summer" is a song by the American singer-songwriter Taylor Swift from her seventh studio album, Lover (2019). Swift and Jack Antonoff produced the song, and they wrote it with St. Vincent. "Cruel Summer" is a synth-pop, industrial pop, and electropop song composed of synths, wobbling beats, and vocoder-manipulated vocals. The lyrics are about an intense romance during a painful summer.

When it was first released as an album track on Lover, music critics praised "Cruel Summer" for its melodic composition and catchy sound, specifically highlighting the hook and bridge. Many deemed it a highlight on Lover and one of Swift's best songs. "Cruel Summer" debuted in the top 30 of various singles charts in 2019 and became a fan favorite over time, prompting fans and publications to question why Swift did not release the track as a single. After being included in the set list of Swift's sixth concert tour, the Eras Tour, in 2023, "Cruel Summer" became viral on social media, leading Republic Records to release it as a single on June 13, 2023.

In the United States, the single peaked atop the Billboard Hot 100 and helped Swift become the solo artist with the most number-one songs on the Pop Airplay and Adult Pop Airplay radio charts. Elsewhere, it topped the Billboard Global 200 and the singles charts in Australia, Canada, the Philippines, and Singapore. It was the seventh-most-streamed song globally of 2023 and was placed on the 2024 revision of Rolling Stone's 500 Greatest Songs of All Time.