Railways in South East Queensland consist of a large passenger and freight rail network centred on Brisbane, the capital city of the Australian state of Queensland. Suburban and interurban passenger rail services are operated by Queensland Rail, which also operates long-distance services connecting Brisbane to the rest of the state. Aurizon and Pacific National are private companies which operate freight services. The passenger rail network in South East Queensland is known as the Citytrain network.

Queensland Rail operates ten suburban and two interurban lines in South East Queensland, all of which are electrified. Centred in the Brisbane central business district, the network extends as far as Gympie in the north, Varsity Lakes in the south, Rosewood in the west, and Cleveland in the east to Moreton Bay.

Each line is ascribed a colour and name on all Queensland Rail signage and marketing collateral including timetables, posters and maps. There are 154 stations on the South East Queensland rail network. Services and ticketing are co-ordinated by the Queensland Government agency Translink.

Queensland Rail’s trains had 42.86 million boardings in the 2022–23 financial year, giving the SEQ rail network the fourth highest patronage out of Australia's suburban rail networks, behind that of Sydney, Melbourne and Perth.

The first railway in Queensland did not actually run to Brisbane, but ran from Ipswich to Grandchester. Opened in July 1865, the line into Brisbane was not completed until the opening of the Albert Bridge in July 1875. Branch lines in the city itself did not start until the next decade, with the branch line to Sandgate opened in May 1882, and the branch from Eagle Junction to Racecourse in September the same year.

Lines were opened from Brisbane to Sandgate and Ascot in 1882. The first section of the North Coast line opened to Petrie in 1888. In 1891 this line was connected to the Maryborough line at Gympie, creating a through line to Mount Perry. A branch line was built from Caboolture to Woodford in 1909 and Kilcoy in 1913, now closed. A branch line was opened from Monkland (south of Gympie) to Brooloo in 1915. A line was opened from the first South Brisbane station at Stanley Street, Woolloongabba to Beenleigh in 1885, and extended to Southport in 1889 and Tweed Heads, New South Wales in 1903. This line was closed beyond Beenleigh in 1964.

A branch line was completed between Park Road station and Cleveland in 1889, although the section beyond Lota station was closed and since reconstructed. A new South Brisbane station was built on Melbourne Street in 1891. This became the terminus of the standard gauge line from Grafton in 1930 and Sydney in 1932. A dual gauge line was built from South Brisbane over the Brisbane River to Roma Street in 1978. A line was opened in 1980 from a junction near Lindum station on the Cleveland line to the Port of Brisbane at Fisherman's Island. This was converted to dual 1435/1067 mm gauge and extended in parallel with the duplicated passenger line to Dutton Park in about 1995 under the Keating government's One Nation program.

The Beaudesert line was opened between Bethania and Beaudesert in 1888, and closed in 1996. The Canungra line was completed to Canungra in 1915, now closed. The line from extended from Roma Street to Central stations in 1889, and to Brunswick Street station in 1890. The Ferny Grove line was opened from a junction at Mayne to Enoggera in 1899. The short Laidley Valley railway lines opened on 19 April 1911 but was never profitable.