Science

• Regret (emotion), an intelligent or emotional dislike for personal past acts and behaviours.
• Regret (decision theory), the difference between expected loss and actual loss

Music

• Regret (song), a song by New Order from the album Republic
• "Regrets," a hip-hop song by Jay-Z from his 1996 debut album Reasonable Doubt
• "Regrets," a song by Ben Folds Five from their 1999 album The Unauthorized Biography of Reinhold Messner
• Regrets (single), the second single from Nicole Wray's Lovechild album
• Regrets (song), a 1991 song by Mylène Farmer and Jean-Louis Murat

Games

• Regret (Halo), One of the Prophets from the game of Halo 2
• Regret, also known as Legretta, one of the Six God Generals from Tales of the Abyss

Other

• Regret (horse), a champion racehorse