O-Negative (Thai: รัก-ออกแบบไม่ได้) is a 1998 Thai romance drama film directed by Pinyo Roothum, and starring Ray MacDonald, Tata Young, Shahkrit Yamnarm, Manaswee Krittanookul, and Sriphan Chunechomboon.

The film follows a group of five college freshmen, all of whom have O-Negative blood, and their experiences with romance and heartbreak.

Prim, Art, Puen, Fun, and Chomphoo are close friends in a group called "Negative," because all five members have blood type O.

It doesn’t have a particularly novel storyline, but the way the film is presented is intriguing and manages to capture the audience’s attention from start to finish.

The film was rebooted into a television series in 2016,[2] and was broadcast in GMM 25 between November 30, 2016 to February 23, 2017.