Major General Sir David Mercer, KCB (1 July 1864 – 1 July 1920) was a Royal Marines officer who served as Adjutant-General Royal Marines.

[1] Mercer was commissioned into the Royal Marine Light Infantry in 1883.

[2] He became commander of the 1st (Royal Naval) Brigade in 1914 and saw action during the Siege of Antwerp.

Following the subsequent retreat, Mercer led the brigade into the Netherlands to avoid capture by the Germans.

[2] The plan had been for Mercer to become military governor of Imbros[3] but, after fierce fighting, he was evacuated from Gallipoli in December 1915.