Boulder was a town in the Western Australian Goldfields 595 kilometres (370 mi) east of Perth and bordering onto the town of Kalgoorlie in the Eastern Goldfields region. Until 1989 it was part of its own municipality. In 1989 the towns of Kalgoorlie and Boulder were merged to form the City of Kalgoorlie-Boulder. After the merger Boulder officially became a suburb of Kalgoorlie-Boulder.
The population of Boulder in 1901 was 2,936 (1850 males and 1086 females) which increased to 5,658 (3090 males and 2568 females) in 1903.
At the 2006 census, Boulder had a population of 5,178.
On 20 April 2010 Kalgoorlie-Boulder suffered a magnitude 5.0 earthquake which damaged several of the historic buildings in Boulder.