John Thayer (1755 – 17 February 1815) was the first native of New England ordained to the Roman Catholic priesthood.
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.
Upon his return to Boston, he established a small chapel in School Street, primarily for French Catholics.
In 1803, he returned to Europe and finally settled in Limerick, Ireland, United Kingdom where he was much more successful in his ministry.