Day One may refer to:
Film Day One (1989 film), a 1989 television film Day One, also known as To Write Love on Her Arms, a 2012 drama film Day One (2015 film), a 2015 short film A Quiet Place: Day One, 2024 film
Television Day One (TV program), a 1993–1995 news magazine program "Day One", a 1994 episode of ER Day 1, the first season of 24 (2001–2002) Day One (TV series), a planned 2009 television pilot "Day One" (Torchwood), a 2006 episode of Torchwood "Day One", a 2009 episode of Torchwood: Children of Earth "Day One" (The Last of Us, a 2025 episode of The Last of Us "Day One" (Doc, a 2025 episode of Doc
Music Day One (band), an English trip hop band Day One (Birds of Tokyo album), a 2007 album by Birds of Tokyo Day One (From Ashes To New album), a 2016 album by From Ashes To New Day One (Sarah Slean album), a 2004 album by Sarah Slean Day One (Snob Scrilla album), a 2009 album by Snob Scrilla Day 1 (album), a 1991 album by Robbie Nevil "Day 1" (song), a song by Leslie Grace "Day 1", a 2015 song by Red Velvet from The Red "Day One", a 2015 song by Matthew West from Live Forever "Day One", a 2015 song by Chris Brown from Royalty "Day One", a 2011 song by Lights from Siberia
Video games Half-Life: Day One, a Half-Life demo Day One: Garry's Incident, a video game by Wild Games Studio Day 1 Studios, an American videogame developer
Other Day One (app), a personal journaling app for iOS, macOS and Android Day One (building), part of Amazon.com's downtown Seattle corporate headquarters Day One Christian Ministries, an organisation promoting Sunday as a day of rest, formerly known as the Lord's Day Observation Society (LDOS) WWE Day 1, a professional wrestling event First of the month, numbered 1 each month