| Unit Name: | 4th Mounted Brigade |
| Dates: | 1914–1916 |
| Type: | Yeomanry |
| Size: | Brigade |
| Battles: | First World War |
The 4th Mounted Brigade previously known as the 2/1st South Wales 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 South Wales Mounted Brigade. It had under command the 2/1st Pembroke Yeomanry, the 2/1st Montgomeryshire Yeomanry, the 2/1st Welsh Horse Yeomanry and the 2/1st Glamorgan Yeomanry. All of which were converted in cyclist units in 1916, the brigade, never having seen any active service, ceased to exist.[1]