The Fencibles (from the word defencible) were British militia regiments raised in the United Kingdom and in the colonies for defence against the threat of invasion during the Seven Years' War, the American War of Independence, the French Revolutionary Wars, the Napoleonic Wars and the War of 1812 in the late 18th and early 19th centuries. Usually temporary units, composed of local volunteers and commanded by Regular Army officers, they were usually confined to garrison and patrol duties, freeing Regular Army units to perform offensive operations. They had no liability for overseas service.
They included naval forces known as "River Fencibles", made up of boatmen on the Thames and other southern English towns and cities, as well as Sea Fencibles, who, among their other duties, manned small commercial vessels converted to coastal defense.
The Scottish Highlands supplied fencible regiments for most of the second half of the 18th century. The first regiment raised was the Argyle Fencibles in 1759 and the last was the MacLeod Fencibles in 1779. In all over 20 regiments were created, although they were not all in existence at the same time. Some Highland fencibles regiments saw action in the Irish Rebellion of 1798, while other performed garrison and policing duties in Britain, Ireland, the Channel Islands and Gibraltar.
The Royal Fencible Americans was a Loyalist unit raised by the British in Nova Scotia in 1775, that successfully withstood an attack by Patriot forces under Jonathan Eddy at the Battle of Fort Cumberland.