The superb fairy wren is a passerine bird in the Australasian wren family, and is common and familiar across south-eastern Australia. The species is sedentary and territorial, also exhibiting a high degree of sexual dimorphism; the male in breeding plumage has a striking bright blue forehead, ear coverts, mantle, and tail, with a black mask and black or dark blue throat. Non-breeding males, females and juveniles are predominantly grey-brown in colour; this gave the early impression that males were polygamous, as all dull-coloured birds were taken for females. Six subspecies groups are recognized: three larger and darker forms from Tasmania, Flinders and King Island respectively, and three smaller and paler forms from mainland Australia and Kangaroo Island.

Like other fairy wrens, the superb fairy wren is notable for several peculiar behavioural characteristics; the birds are socially monogamous and sexually promiscuous, meaning that although they form pairs between one male and one female, each partner will mate with other individuals and even assist in raising the young from such pairings. Male wrens pluck yellow petals and display them to females as part of a courtship display.

The superb fairy wren can be found in almost any area that has at least a little dense undergrowth for shelter, including grasslands with scattered shrubs, moderately thick forest, woodland, heaths, and domestic gardens. It has adapted well to the urban environment and is common in suburban Sydney, Canberra and Melbourne. The superb fairy wren eats mostly insects and supplements its diet with seeds.

The superb fairy wren is 14 cm (5 1⁄2 in) long[ and weighs 8–13 g (0.28–0.46 oz), with males on average slightly larger than females.The average tail length is 5.9 cm (2 1⁄3 in),among the shortest in the genus.[31] Averaging 9 mm (0.4 in) in subspecies cyaneus and 8 mm (0.3 in) in subspecies cyanochlamys,[ the bill is relatively long, narrow and pointed and wider at the base. Wider than it is deep, the bill is similar in shape to those of other birds that feed by probing for or picking insects off their environs.

Like other fairy wrens, the superb fairy wren is notable for its marked sexual dimorphism, males adopting a highly visible breeding plumage of brilliant iridescent blue contrasting with black and grey-brown. The brightly coloured crown and ear tufts are prominently featured in breeding displays.[33] The breeding male has a bright-blue forehead, ear coverts, mantle and tail, brown wings, and black throat, eye band, breast and bill. Females, immatures, and non-breeding males are a plain fawn colour with a lighter underbelly and a fawn (females and immatures) or dull greyish blue (males) tail. The bill is brown in females and juveniles and black in males after their first winter. Immature males moult into breeding plumage the first breeding season after hatching, though incomplete moulting sometimes leaves residual brownish plumage that takes another year or two to perfect. Both sexes moult in autumn after breeding, with males assuming an eclipse non-breeding plumage. They moult again into nuptial plumage in winter or spring. Breeding males' blue plumage, particularly the ear-coverts, is highly iridescent because of the flattened and twisted surface of the barbules.The blue plumage also reflects ultraviolet light strongly, and so may be even more prominent to other fairy wrens, whose colour vision extends into this part of the spectr