The Territorial and Reserve Forces Act 1907 was an Act of the Parliament of the United Kingdom that reformed the auxiliary forces of the British Army by transferring existing Volunteer and Yeomanry units into a new Territorial Force (TF); and disbanding the Militia to form a new Special Reserve of the Regular Army. This reorganisation formed a major part of the Haldane Reforms, named after the creator of the Act, Richard Haldane.

The Volunteer Force was a citizen army of part-time rifle, artillery and engineer corps, created as a popular movement throughout the British Empire in 1859. Originally highly autonomous, the units of volunteers became increasingly integrated with the British Army after the Childers Reforms in 1881, before forming part of the Territorial Force in 1908. Most of the regiments of the present Army Reserves Infantry, Artillery, Engineers and Signals units are directly descended from Volunteer Force units.