Sir Thomas Armstrong (15 June 1898 – 26 June 1994) was an English organist, conductor, composer and educationalist. He was from a musical family and his early career was as a church and cathedral organist. From the 1920s onwards he was a broadcaster for the BBC giving talks as well as playing.

While organist and faculty member of Christ Church, Oxford Armstrong combined academic work with practical musicianship, as player and conductor. From 1955 to 1968 he was principal of the Royal Academy of Music (RAM), London, where he was known for his concern for the well-being of his staff and students and his efforts to strengthen links with overseas music colleges.