Balmain Colliery was a coal mine located in Birchgrove in the inner-west of Sydney, in the state of New South Wales, Australia.

[1] At approximately 800 metres (2,600 ft) in depth, it remains the deepest coal mine ever to have been sunk in Australia.

The presence of coal was confirmed in 1891 with bores at Birchgrove and Cremorne Point.

[4] Sydney Harbour Collieries (Limited) started the mine, however the company was wound up in 1896;[5] and the mine was bought by the Harbour Collieries Co. Two shafts, named Birthday and Jubilee, were sunk between 1897 and 1902.

Three fatal accidents occurred at the mine claiming ten lives: