Sir Martin le Marchant Hadsley Gosselin, GCVO, KCMG, CB (2 November 1847 – 26 February 1905) was a British diplomat who held the office of Envoy Extraordinary and Minister Plenipotentiary to Portugal.

Educated at Eton College and at Christ Church, Oxford, he entered the diplomatic service in 1868, and after working in the Foreign Office was appointed attaché at Lisbon in 1869.

Later in that year he was one of the British delegates at the conference held by representatives of Great Britain, Germany, and Italy to discuss and fix the duties to be imposed on imports in the conventional basin of the Congo, and he signed the agreement which was arrived at in December 1890.

In April 1892 he was promoted to be secretary of embassy at Madrid, was transferred to Berlin in the following year, and to Paris in 1896, receiving at the latter post the titular rank of minister plenipotentiary.

The arrangement arrived at by the commission was embodied in a convention signed at Paris on 14 June 1898, and provided a solution of questions which had gravely threatened the good relations between the two countries.