AC1 may refer to:
AC1, a ranking grading within the Royal Air Force between 1919 and 1964 AC1, a candidate phylum of bacteria AC1, a complexity class in circuit complexity AC1 Sentinel, an Australian cruiser tank AC-1, an IEC Utilization Category Action Comics #1, containing the first appearances of several superheroes Atlantic Crossing 1, an optical submarine telecommunications cable system Assassin's Creed (video game), the first game in the Assassin's Creed series The Shady Dragon Inn, a Dungeons & Dragons accessory with the code AC1