The 17th Mounted Brigade previously known as the 2/1st Welsh Border Mounted Brigade was a second line yeomanry brigade of the British Army during the First World War. Raised after the declaration of war, it was a mirror formation of the first line Welsh Border Mounted Brigade. It had under command the 2/1st Cheshire Yeomanry, the 2/1st Shropshire Yeomanry, the 2/1st Denbighshire Hussars and the 2/1st Lancashire Hussars. All of which were converted in cyclist units in 1916, the brigade, never having seen any active service, ceased to exist.