Alexander MacFarlane, FRS (c. 1702 – 23 August 1755) was a Scottish merchant, planter and astronomer. After graduating from the University of Glasgow in 1728, he emigrated to the British colony of Jamaica and became a prominent landowner and political figure. MacFarlane was appointed the colony's first Postmaster General in 1735 and elected to the House of Assembly of Jamaica for Saint Elizabeth Parish in 1754. At the time of his death, he owned multiple sugar plantations and nearly 800 slaves.
MacFarlane was also an amateur astronomer who constructed observatories in Port Royal and Kingston, equipped with a variety of instruments purchased from fellow astronomer Colin Campbell. His astronomical observations, though limited in scope, resulted in MacFarlane being elected as a fellow of the Royal Society in 1746. Upon his death, he bequeathed his scientific instruments to the University of Glasgow, where they formed the basis of the Macfarlane Observatory, the first of its kind in Britain. In the 21st century, his legacy has come under scrutiny due to MacFarlane's ownership of slaves.