John Joseph Cassidy MM (14 February 1894 – 21 July 1949) was a Scottish professional footballer who played as an inside left or centre forward. His career was mainly associated with Celtic – he played for the club between 1912 and 1924, although his football career was interrupted by the First World War, during which he served in the British Army in the Black Watch (Royal Highlanders) 1/7th Fife Battalion and won the Military Medal, which led to him being nicknamed "Trooper Joe". He also played for several other Scottish clubs, in England with Bolton Wanderers, in Wales (albeit in the English Football League) with Cardiff City, and on both sides of the border in Ireland with Ballymena and Dundalk. He represented Scotland four times.