Penfield Reef Lighthouse is a lighthouse in Connecticut, United States, on Penfield Reef at the south side of Black Rock Harbor entrance on the Long Island Sound, off the coast of Fairfield, Connecticut. Constructed in 1874, it was one of the last offshore masonry lights. Most offshore lights built after this were cast iron towers built on cylindrical cast iron foundations. Penfield Reef has been called one of the most treacherous areas of western Long Island Sound. The structure is about 1.1 miles (1.8 km) off Fairfield Beach, on one end of the reef.
The lighthouse's foundation, structure and roofs were in good condition, according to a 2004 Town of Fairfield report, but the wood frame supporting the balcony around the tower was in need of major repairs. Other problems include asbestos tiles on the floor, lead paint on the walls, mold in most places and decaying brick and mortar work in the basement. The U.S. Coast Guard last had the lighthouse repaired in 2003. The lighthouse is connected to a two-floor keeper's quarters built of granite and timber frames on a concrete foundation surrounded by rocks. The Penfield Reef Light was constructed in 1874. The light is an active aid to navigation.