Lieutenant-General Francis Humberston Mackenzie, 1st Baron Seaforth, FRS, FRSE, FLS (9 June 1754 – 11 January 1815) was a British politician, soldier, and botanist.

During his tenure he reformed slavery on the island, implemented a prohibition on killing slaves, and reduced official discrimination against free blacks.

[2] In 1794, Seaforth was elected a Fellow of the Royal Society for his contributions to botany, with the genus Seaforthia named in recognition of his work.

A year later, In 1795, he was elected a Fellow of the Royal Society of Edinburgh, again in acknowledgement of his contributions to botany: his proposers were Daniel Rutherford, Alexander Monro (secundus), and John Playfair.

Lord Seaforth commissioned Benjamin West's 1786 painting Alexander III of Scotland Rescued from the Fury of a Stag by the Intrepidity of Colin Fitzgerald.

[9]Seaforth nearly recovered entirely the use of his tongue, but during the last two years of his life, which he spent mourning the deaths of his four sons, he rarely spoke.