Justin Cathal Geever, known professionally as Justin Sane, is an American singer and guitarist. He was the lead guitarist, singer and songwriter of Anti-Flag, a punk rock band formed in 1988 in Pittsburgh, Pennsylvania that was known for its left-wing political views. Sane holds US and Irish citizenship and lived in Pittsburgh.

Anti-Flag was an American punk rock band formed in Pittsburgh, Pennsylvania, in 1988. The band was known for its left-wing political activism. For the majority of the band's career, their members included Justin Sane, Chris Head (guitar), Pat Thetic (drums), and Chris Barker, also known as Chris No. 2.