Sir Gilbert Mackereth KCMG MC (19 October 1892 – 11 January 1962) was a decorated British Army officer of the First World War who subsequently served as a British diplomat, most notably as Ambassador to Colombia from 1947 to 1953. He began his army service in the ranks in 1914 but after being commissioned in 1916 rapidly rose through the ranks and became a battalion commander. As a subaltern he was decorated for the rescue of a group of soldiers under heavy fire in 1917.