A retrofit LED canopy luminaire assembly is provided that is configured for mounting with a canopy fixture supported by a canopy deck and having a fixture base located beneath the canopy deck, a lamp socket housing operatively connected to, and extending upwardly from the fixture base and through the canopy deck, and a ballast housing located above the canopy deck and operatively connected to the lamp socket housing. The retrofit LED canopy luminaire assembly includes a retrofit adapter bracket, a retrofit LED canopy luminaire configured to be mounted to the retrofit adapter bracket, and a wire guide body supported within the lamp socket housing that is configured to route electrical leads extending outwardly from the retrofit LED canopy luminaire through the wire guide body and into the ballast housing.