5. c. 104) was an act passed by the Parliament of the United Kingdom during the First World War to impose conscription in Great Britain, but not in Ireland or any other British jurisdiction.

Previously the British Government had relied on voluntary enlistment, and latterly a kind of moral conscription called the Derby Scheme.

[2] The Act specified that men from 18 to 41 years old were liable to be called up for service in the army unless they were eligible for exemptions listed under this Act, including men who were married, widowed with children, serving in the Royal Navy, a minister of religion, or working in one of a number of reserved occupations, or for conscientious objection.

These tribunals had powers to grant exemption from service, usually conditional or temporary, under the eligibility criteria which for the first time in history included conscientious objection.

Due to political considerations, the Military Service Act of 1916 applied only to male British subjects ordinarily resident in Great Britain.