| Unit Name: | Royal Marine Brigade 3rd (Royal Marine) Brigade |
| Dates: | 7–19 July 1916 |
| Country: |  United Kingdom |
| Type: | Infantry |
| Size: | Brigade of 1,500 men |
| Command Structure: | Royal Naval Division |
| Garrison: | Portsmouth Naval Base, Portsmouth |
| Garrison Label: | Brigade HQ |
| Battles: | |
| Identification Symbol Label: | Metal divisional badge |
The 3rd (Royal Marine) was an infantry brigade of the Royal Marines. It was assigned to the 63rd (Royal Naval) Division and served on the Western Front during the First World War.
The brigade then known as the Royal Marine Brigade, was raised in August 1914, from surplus naval reserves. On 2 August 1915, the brigade was reduced from four to two battalions and transferred to the 2nd Royal Naval Brigade. The Royal Marine Brigade was then disbanded. In May 1916, the Royal Marine Brigade was reformed. In July 1916, it was re-designated the 1st (Royal Naval) Brigade and then the 188th Brigade later the same month.
The infantry battalions did not all serve at once, but all were assigned to the brigade during the war.