The present disclosure discloses a lamp for projecting a nebula and a starry sky comprising a housing, a light source assembly, a laser assembly, a rotating assembly, a control board, a base seat, and a power source port. The light source assembly and the laser assembly are disposed in the housing and penetrate through the housing, and the rotating assembly and the control board are disposed in the housing. The rotating assembly is configured to drive a rotating optical sheet and a diffraction sheet to rotate. The light source assembly comprises a light source board, a light reflecting cup, the rotating optical sheet, and a lens assembly having a frosted surface with an array of protrusions. The light source board, the light reflecting cup, the rotating optical sheet, and the lens assembly are successively disposed along a path in which light rays emitted by the light source board move.