The regiment was raised in 1793 as a volunteer corps in Shropshire, and taken into the British Army the following year as the 86th (Shropshire Volunteers). In 1795, after the Battle of Groix it absorbed the remnants of the disbanded 118th Regiment of Foot (Fingall's Regiment), which had been raised in 1794 for service as marines. In 1806 it became the 86th (Leinster) Regiment of Foot, and then in 1812 it was renamed as the 86th (Royal County Down) Regiment of Foot.