Garden architect. Mackenzie was the third son of Sir Francis Mackenzie, the laird of Gairloch. He spent much of his youth on the continent. His elder brother inherited the Gairloch Estate but, with the help of his mother, Mackenzie purchased the 4860 ha (12,000 acre) Inverewe and Kernsary Estate in 1862. He proceeded to build Inverewe House and landscape the surrounding land to create the remarkable Inverewe Garden. This is noted for its exotic species, growing at a latitude equivalent to southern Greenland.
Mackenzie's daughter, Mrs Mairi Saywer, gave the garden to the National Trust for Scotland just before her death in 1953.