Billabong (// BIL-ə-bong) is an Australian term for an oxbow lake, an isolated pond left behind after a river changes course. Billabongs are usually formed when the path of a creek or river changes, leaving the former branch with a dead end. As a result of the arid Australian climate in which these "dead rivers" are often found, billabongs fill with water seasonally but can be dry for a greater part of the year.
The etymology of the word billabong is disputed. The word is most likely derived from the Wiradjuri term bilabaŋ, which means "a watercourse that runs only after rain". It is derived from bila, meaning "river", It may have been combined with bong or bung, meaning "dead". One source, however, claims that the term is of Scottish Gaelic origin.
Billabongs were significant because they held water longer than parts of rivers; it was important for people to identify and name these areas.
Once a jolly swagman camped by a billabong,
Under the shade of a coolibah tree,
And he sang as he watched and waited till his billy boiled,
Who'll come a'waltzing Matilda with me
Both Aboriginal Australians and European artists use billabongs as subject matter in painting. For example, Aboriginal painter Tjyllyungoo (Lance Chad) has a watercolour entitled Trees at a billabong.
American avant-garde filmmaker Will Hindle produced a short film titled Billabong in 1969.
Billabong is the name of an Australian brand of sportswear for surf, skateboard, and snowboard.