Fort Lytton, Military fortress in Brisbane, Australia.

Fort Lytton is a military fortress located at the mouth of the Brisbane River with gun emplacements, barracks, and storage structures built in the colonial era. The site contains multiple defensive buildings and exhibits arranged across the grounds, showing how such installations were designed and organized.

Fort Lytton was built in 1880–1882 to stop a feared naval attack on Brisbane by Russia or France. Designed by Lieutenant-Colonel Peter Scratchley, it guarded the Brisbane River mouth with a remote-controlled minefield and four muzzle-loading guns. In 1888 two 6-inch disappearing guns replaced the 80-pounders, and two Hotchkiss 6-pounder quick-firing guns were added in 1893. The minefield closed in 1908; the disappearing guns stayed in use until 1938.

The name Fort Lytton also refers to the one-square-mile military base that surrounded the fort. For its first forty years the fort was Queensland's main training base for reserve soldiers, with up to 5,000 reservists attending the annual "Easter Encampment". Today guided tours are run by the Fort Lytton Historical Association, a non-profit volunteer organisation.

The fort is open to visitors on certain days and offers guided tours to help you learn about the military history. The best way to explore the grounds is on foot, so allow enough time to thoroughly see all the buildings and exhibits.

The minefield across the river mouth was closed in 1908, but the two 6-inch 100-pdr breech-loading disappearing guns installed in 1888 stayed in service until 1938. Lytton Hill, about 1.2 km east of the fort, held a redoubt linked to it by telegraph and watched ship movements in Moreton Bay.