Fremantle Prison, sometimes referred to as Fremantle Gaol or Fremantle Jail, is a former Australian prison and World Heritage Site in Fremantle, Western Australia. The site includes the prison cellblocks, gatehouse, perimeter walls, cottages, and tunnels. It was initially used for convicts transported from Britain, but was transferred to the colonial government in 1886 for use for locally-sentenced prisoners. Royal Commissions were held in 1898 and 1911, and instigated some reform to the prison system, but significant changes did not begin until the 1960s. The government department in charge of the prison underwent several reorganisations in the 1970s and 1980s, but the culture of Fremantle Prison was resistant to change. Growing prisoner discontent culminated in a 1988 riot with guards taken hostage, and a fire that caused $1.8 million worth of damage. The prison closed in 1991, replaced by the new maximum-security Casuarina Prison.

Fremantle is a port city in Western Australia located at the mouth of the Swan River in the metropolitan area of Perth, the state capital. Fremantle Harbour serves as the port of Perth. The Western Australian vernacular diminutive for Fremantle is Freo.