John Welsh of Ayr (1568-1622) was a Scottish Presbyterian leader. He was born in Dumfriesshire, and, after a wayward youth, attended the University of Edinburgh and obtained his MA in 1588. He became a minister in Selkirk, Scotland, and married a daughter of John Knox.

Welsh later ministered in Kirkcudbright and in Ayr, where he spent five years and with which he was ever afterwards associated. His preaching resulted in imprisonment on the orders of King James VI of Scotland, and in 1606 he was exiled to France, where he continued his activities for many years. His grandson was the Covenanters' leader, John Welsh of Irongray.