Cyanothamnus coerulescens, commonly known as blue boronia,[2] is a plant in the citrus family, Rutaceae and is endemic to southern Australia.

The flowers are bright blue, lilac-coloured or white and are arranged singly in leaf axils or in dense, leafy spikes on the end of the branches.

[6][7] In a 2013 paper in the journal Taxon, Marco Duretto and others changed the name to Cyanothamnus bussellianus on the basis of cladistic analysis.

[8] The specific epithet (coerulescens) is a Latin word caeruleus meaning "sky blue"[9] with the ending -escens signifying "beginning of" or "becoming".

[2][3][5][13] All three subspecies of C. coerulescens are classified as "not threatened" by the Western Australian Government Department of Parks and Wildlife.