John Thayer (1755 – 17 February 1815) was the first native of New England ordained to the Roman Catholic priesthood. He was born in Boston, Massachusetts. Thayer was educated at Yale College and was a Protestant in his early life. He was ordained as a Congregationalist minister and served as a chaplain during the American Revolutionary War. While visiting Rome in 1783, he converted to the Roman Catholic faith, an act which caused a sensation in New England at the time. He credited his conversion to miracles attributed to the noted mendicant, Saint Benedict Joseph Labre, who lived and died there in that period.