Abstract: A low-profile fluorescent luminaire for attachment to a suspended ceiling and methods for retrofitting the luminaire to an existing lighting system. The low-profile fluorescent luminaire has lightweight “I”-shaped framework comprising a pair of transversely-extending end plates attached adjacent to opposed longitudinal ends of a longitudinally-extending spine. The spine and the end plates have a substantially coplanar arrangement to provide a low-profile structure that closely conforms to the ceiling. The “I”-shaped framework supports a reflector positioned below the spine and end plates when the luminaire is in a supported functional position. The low-profile luminaire can be retrofitted to a suspended ceiling to replace the existing light fixtures or to supplement the light output of an existing lighting system without modifying or removing the existing lighting fixtures.