Melaleuca osullivanii is a plant in the myrtle family, Myrtaceae and is endemic to the south-west of Western Australia. It was first formally described in 2004 after a review of the broombush group, Melaleuca uncinata. It differs from others in the group by having leaves that are fine and circular in cross section. The closest other broombrush is Melaleuca hamata whose leaves are 0.8–1.6 mm (0.03–0.06 in) in diameter compared to 0.7–0.9 mm (0.03–0.04 in) for this species.