Dr. John Macadam (May 1827 – 2 September 1865), was a Scottish-Australian chemist, medical teacher and politician. The genus Macadamia was named after him in 1857 by his colleague Ferdinand von Mueller.

John Loudon McAdam (born John Lowdon McAdam, 23 September 1756<ref name="OPR /> – 26 November 1836) was a Scottish engineer and road-builder. He invented a new process, "macadamisation", for building roads with a smooth hard surface, using controlled materials of mixed particle size and predetermined structure, that would be more durable and less muddy than soil-based tracks.