Mass effect may refer to: * Mass Effect, a series of action role-playing video games. * Mass Effect, the first game in the series. * Mass Effect 2, the second game in the series. * Mass Effect 3, the third game in the series. * In the Mass Effect universe, “mass effect” is a physics phenomenon adapted from what real life scientists call dark energy that has properties along the lines of other physics forces such as gravity and electromagnetism. * Mass effect (medicine), the effect of a growing mass or tumor.