The 1st Light Horse Brigade was a mounted infantry brigade of the Australian Imperial Force (AIF), which served in the Middle Eastern theatre of World War I. The brigade was initially formed as a part-time militia formation in the early 1900s in New South Wales and then later in Queensland. In 1914, the brigade was re-constituted as part of the AIF and was sent to Egypt. Forming part of the New Zealand and Australian Division, during the Gallipoli Campaign it served in a dismounted role between May and December 1915. After being withdrawn to Egypt it served in the Anzac Mounted Division from March 1916 as part of the Egyptian Expeditionary Force, taking part in the Sinai and Palestine Campaign until the end of the war. It was disbanded in 1919. After the war, the AIF light horse regiments