The Royal Sussex Militia Artillery was a part-time reserve unit of Britain's Royal Artillery from the County of Sussex, which served from 1853 to 1909.

The Royal Sussex Light Infantry Militia, later the 3rd Battalion, Royal Sussex Regiment, was an auxiliary regiment raised in Sussex on the South Coast of England. From its formal creation in 1778 the regiment served in home defence in all of Britain's major wars. It saw active service during the Second Boer War, and trained thousands of reinforcements during World War I. After a shadowy postwar existence it was formally disbanded in 1953