O Negative refers to blood group O, Rh-negative, in the ABO and Rh blood group systems.
O Negative may also refer to:
O−, an oxygen ion with a charge of -1 O-Negative (1998 film), a 1998 Thai film O-Negative (TV series), a 2016 Thai TV series adaptation of the 1998 film O Negative (2015 film), a 2015 Canadian short film Type O Negative, an American heavy metal band