A pool light adapter ring for retrofitting a pool light in a pool wall niche. The adapter ring has a pair of interlocking hooks to allow the ring to be compressed to a first, compressed state, inserted into a wall niche and then relaxed to a second, rigid state. The adapter ring has mounting brackets attached to the ring for receipt of a pool light or other device. The adapter ring also has a plurality of anchor screws for securing the adapter ring inside the niche. Further, some embodiments may include a grounding screw for attaching the grounding wire from the pool light.