The Colonial Secretary of Western Australia was one of the most important and powerful public offices in Western Australia, in the time when Western Australia was a British colony. The Colonial Secretary was the representative of the British Colonial Office in Western Australia, and was usually appointed from Britain. He was responsible for all official correspondence between the colony and the Colonial Office. He was at all times a member of the Western Australian Legislative Council and the Western Australian Executive Council.

After Western Australia gained responsible government in 1890, the office of Colonial Secretary became a ministerial portfolio. The responsibilities of the office changed substantially, and it was no longer such an important role. Colebatch (2004) described the office of Colonial Secretary in 1917 as

responsible for a large number of departments including Aborigines, Public Health, charities and many of the state trading concerns including the State Shipping Service. The position required a great deal of detailed work and would always attract many Parliamentary Questions, but did not allow the minister much scope for initiative or achievement.

Since Western Australia was no longer a British colony after 1901, the office of Colonial Secretary was misnamed after this date. In 1924, the office was renamed to Chief Secretary.

The following is a list of colonial secretaries of Western Australia: