Yannathan, a rural locality, is on the edge of the former Koo Wee Rup Swamp and is 9 km north-east of Lang Lang. The topography is undulating to flat, and before drainage works were carried out farmlands could be waterlogged when the Lang Lang River flooded.
Farm selections began in the Yannathan district in the late 1870s. According to Bunce's Language of the Aborigines of the Colony of Victoria (1859) Yannathan is an Aboriginal word meaning jaunt, move or walk about.
A school opened in 1882, and eight years later local families decided to construct a multi-denominational church rather than a public hall. The Union church (Anglican, Methodist and Presbyterian) opened in 1890. A post office had opened in 1884 and a general store was added in 1898. A long awaited public hall came in 1902.
Yannathan had dairying and potato growing, and a local butter factory operated from 1900 until 1930. A branch line from Koo Wee Rup station ran from 1922 until 1950, and rail carriage of dairy produce to larger factories replaced the local producer.
Reticulated electricity was switched on in 1936.
Yannathan has a recreation reserve with tennis courts, a public hall and the Union church. Its census populations have been:
Neil Gunson, The good country: Cranbourne Shire, 1968
Fred Hooper, We on earth hath union: a history of the Yannathan Union church (1890-1990), 1990