The Guards Machine Gun Regiment was formed from units of the Household Cavalry and Cavalry of the Line. This took place on the 10th May 1918. The units transferred were:
| Battalion of G.M.G.R. | Original Unit |
| 1st | 1st Life Guards |
| 2nd | 2nd Life Guards |
| 3rd | Royal Horse Guards |
| 4th | 1st Gds Bde MG Coy |
| 2nd Gds Bde MG Coy | |
| 3rd Gds Bde MG Coy | |
| 4th Gds Bde MG Coy |