A mounting adaptor for an electric light fixture to be mounted on a surface. The mounting adaptor comprising: a base and a joining member each having an interfacing face, one of the base and the joining member comprising on its interfacing face a groove, the other one of the base and the joining member comprising on its interfacing face a lip adapted to cooperate with the groove thereby providing a capability to assemble releasably the joining member with the base; a locking mechanism adapted to lock the base and the joining member in a mounted position relatively to each other; the base comprising a mounting element adapted to mount the base to the surface; and the joining member comprising a joint element adapted to mount the electric light fixture to the joining member.