The 100th Light Anti-Aircraft Regiment, Royal Artillery, (100th LAA Rgt) was an air defence unit of the British Army during World War II. Initially raised as an infantry battalion of the Royal Fusiliers (City of London Regiment) in 1940, it transferred to the Royal Artillery in 1941. It served with 56th (London) Infantry Division in the final stages of the Tunisian Campaign, in the landings at Salerno and subsequent fighting in Italy, including the Battle of Anzio, until it was disbanded at the beginning of 1945.