The Twins Effect, also known as Vampire Effect in the United States, is a 2003 Hong Kong film directed by Dante Lam and Donnie Yen. The film was derived from Cantopop group Twins, starring both members Charlene Choi and Gillian Chung in the leading roles. Co-stars include Edison Chen and Ekin Cheng. Jackie Chan makes a cameo appearance as an ambulance driver.

Following its release on 8 March 2003, The Twins Effect was a box-office success in Hong Kong, became the highest grossing domestic film of the year. The film gained huge popularity, mainly from fans of Twins.