Joseph Bertram Sleeman (21 June 1885 – 6 July 1970) was an Australian politician who was a Labor Party member of the Legislative Assembly of Western Australia from 1924 to 1959, representing the seat of Fremantle.

He and his parents moved to Western Australia in 1895, and he attended school in Day Dawn, a mining town in the state's Mid West.

[1] At the 1924 state election, he stood for the seat of Fremantle, and defeated the sitting Nationalist member, Frank Gibson.

Only two other speakers have served for longer periods – Sir James Lee-Steere and John Hearman.

[3] Sleeman continued in parliament until his retirement at the 1959 election, having spent nearly 35 years as the member for Fremantle.