The didgeridoo (/ˌdɪdʒəriˈduː/ ^ⓘ; spelt didjeridu; among other variants) is a wind instrument, played with vibrating lips to produce a continuous drone while using a special breathing technique called circular breathing. The didgeridoo was developed by Aboriginal peoples of northern Australia at least 1,000 years ago, and is now in use around the world, though still most strongly associated with Indigenous Australian music. In the Yolŋu languages of the indigenous people of northeast Arnhem Land the name for the instrument is the yiḏaki, or more recently by some, mandapul. In the Bininj Kunwok language of West Arnhem Land it is known as mako (pronounced, and sometimes spelt, as mago).

A didgeridoo is usually cylindrical or conical, and can measure anywhere from 1 to 3 m (3 to 10 ft) long. Most are around 1.2 m (4 ft) long. Generally, the longer the instrument, the lower its pitch or key. Flared instruments play a higher pitch than unflared instruments of the same length.

There are no reliable sources of the exact age of the didgeridoo. Archaeological studies suggest that people of the Kakadu region in Northern Australia have been using the didgeridoo for less than 1,000 years, based on the dating of rock art paintings. A clear rock painting in Ginga Wardelirrhmeng, on the northern edge of the Arnhem Land plateau, from the freshwater period (that had begun 1500 years ago) shows a didgeridoo player and two song-men participating in an Ubarr ceremony. It is thus thought that it was developed by Aboriginal peoples of northern Australia, possibly in Arnhem Land.

T. B. Wilson's Narrative of a Voyage Round the World (1835) includes a drawing of an Aboriginal man from Raffles Bay on the Cobourg Peninsula (about 350 kilometres (220 mi) east of Darwin) playing the instrument. Others observed such an instrument in the same area, made of bamboo and about 3 feet (0.9 m) long. In 1893, English palaeontologist Robert Etheridge, Junior observed the use of "three very curious trumpets" made of bamboo in northern Australia. There were then two native species of bamboo growing along the Adelaide River, Northern Territory".

According to A. P. Elkin, in 1938, the instrument was "only known in the eastern Kimberley [region in Western Australia] and the northern third of the Northern Territory".

The name didgeridoo is not of Aboriginal Australian linguistic origin and is considered to be an onomatopoetic word. The earliest occurrences of the word in print include a 1908 edition of the Hamilton Spectator referring to a "'did-gery-do' (hollow bamboo)", a 1914 edition of The Northern Territory Times and Gazette, and a 1919 issue of Smith's Weekly, in which it was referred to as a "didjerry" and was said to produce the sound "didjerry, didjerry, didjerry and so on ad infinitum".

A rival explanation, that didgeridoo is a corruption of the Irish phrase dúdaire dubh or Scottish Gaelic dùdaire dúth, is controversial. Irish dúdaire or dúidire, and Scottish Gaelic dùdaire, are nouns that, depending on the context, may mean "trumpeter", "hummer", "crooner" or "puffer", while Irish dubh means "black", and Scottish Gaelic dúth means "native".

There are numerous names for the instrument among the Aboriginal peoples of northern Australia, none of which closely resemble the word "didgeridoo" (see below). Some didgeridoo enthusiasts, scholars and Aboriginal people advocate using local language names for the instrument.