Great Trek, a migration of Boers from Cape Colony into the South African interior during the 1830's and 1840's. The Boers—white settlers in the region who were primarily of Dutch descent—opposed British rule, which had been imposed on them in 1815. Opposition to the British grew when English settlers began arriving in 1820 and when the British abolished slavery in 1834.
The Great Trek began in 1836, and over the next decade some 18,000 Boers left Cape Colony. Those making the migration became known as voortrekkers. The Boers established the independent republics of Natalia (1839), Transvaal (1852), and Orange Free State (1854).