J. Douglas MacMillan (1933–1991) was a Christian minister in the Free Church of Scotland. MacMillan was born the youngest of six children, on the Ardnamurchan peninsula in Argyll. He was converted at the age of 21, and studied at the University of Aberdeen and at the Free Church College. After his ordination, he ministered at St. Columba in Aberdeen (1966–1974) and St Vincent Street in Glasgow (1974–1982), before taking up an appointment as Professor of Church History at the Free Church College.
Since 1994, the biennial MacMillan Lecture in Evangelism has been held at that institution in his honour.