The slender-billed thornbill (Acanthiza iredalei) is a small bird native to Australia.
The thornbill ranges from 9 to 10 cm in length. The colour of its back ranges from olive-grey to a darker olive-brown. The base of its tail is olive-yellow. Its underbelly is a smooth cream colour, and it has a dark bill and pale eyes.
The slender-billed thornbill is rarely observed alone. They are usually seen in flocks of approximately eight birds or in pairs. Thornbill nests are small and built in low shrubs. They are constructed of grass, bark, cobwebs, and other shrubland debris. Females lay up to three eggs during the breeding season, which runs from July until November.