The red-backed fairywren (Malurus melanocephalus) is a species of passerine bird in the Australasian wren family, Maluridae.

It is endemic to Australia and can be found near rivers and coastal areas along the northern and eastern coastlines from the Kimberley in the northwest to the Hunter Region in New South Wales.

The male adopts a striking breeding plumage, with a black head, upperparts and tail, and a brightly coloured red back and brown wings.

It can be nomadic in areas where there are frequent bushfires, although pairs or small groups of birds maintain and defend territories year-round in other parts of its range.

The red-backed fairywren is sexually promiscuous, and each partner may mate with other individuals and even assist in raising the young from such pairings.

The red-backed fairywren was first collected from the vicinity of Port Stephens in New South Wales and described by ornithologist John Latham in 1801 as the black-headed flycatcher (Muscicapa melanocephala); its specific epithet derived from the Ancient Greek μέλας, melas 'black' and κεφαλή, kephalē 'head'.

A male in full adult plumage was described as Sylvia dorsalis, and the explorers Nicholas Aylward Vigors and Thomas Horsfield gave a third specimen from central Queensland the name Malurus brownii, honouring botanist Robert Brown.

John Gould described Malurus cruentatus in 1840 from a short-tailed scarlet-backed specimen collected in Northwestern Australia by Benjamin Bynoe aboard HMS Beagle on its third voyage.

[7] More recently, DNA analysis has shown that the family Maluridae is related to both the Meliphagidae (honeyeaters), and the Pardalotidae (pardalotes, scrubwrens, thornbills, gerygones and allies) within the large superfamily Meliphagoidea.

[10] Termed the bicoloured wrens by ornithologist Richard Schodde, these three species are notable for their lack of head patterns and ear tufts, and solid-coloured black or blue plumage with contrasting shoulder or wing colour; they replace each other geographically across northern Australia and New Guinea.

[11] George Mack, ornithologist of the National Museum of Victoria, was the first to classify the three forms melanocephalus, cruentatus and pyrrhonotus as one species,[12] although Richard Schodde reclassified pyrrhonotus as a hybrid from a broad hybrid zone in North Queensland; this area is bounded by the Burdekin, Endeavour and Norman Rivers.

Breeding males of intermediate plumage, larger and scarlet-backed, or smaller and orange-backed, as well as forms that resemble one of the two parent subspecies, are all encountered within the hybrid zone.

[13] The distribution of the three bi-coloured fairywren species indicates their ancestors lived across New Guinea and northern Australia in a period when sea levels were lower and the two regions were joined by a land bridge.

[18] A 2017 genetic study using both mitochondrial and nuclear DNA found the ancestors of the red-backed and white-shouldered fairywrens diverged from each other around 3 million years ago, and their common ancestor diverged around 5 million years ago from a lineage that gave rise to the white-winged fairywren.

[20] Wider than it is deep, the bill is similar in shape to those of other birds that feed by probing or picking insects off of their environs.

[25] Geographically, it follows Gloger's rule; female birds have whiter bellies and paler brown upperparts inland in sunnier climates.

Its range extends all the way down the east coast east of the Great Dividing Range to the Hunter River in New South Wales,[29] preferring wet, grassy tropical or sub-tropical areas, with tall grasses such as blady grass (Imperata cylindrica), species of Sorghum, and Eulalia.

[35] Both the male and female adult red-backed fairywren may utilise the rodent-run display to distract predators from nests with young birds.

The head, neck and tail are lowered, the wings are held out and the feathers are fluffed as the bird runs rapidly and voices a continuous alarm call.

[44] It can be found hunting for insects in leaf litter, shrubbery and on the edges of bodies of water, mostly in the morning and late afternoon.

[26] Adults and their young may be preyed upon by mammals such as the feral cat and red fox, reptiles such as goannas, rodents,[26] and native predatory birds, such as the Australian magpie, butcherbird species, blue-winged kookaburra, crows and ravens, and shrike-thrushes.