Thomas Roseingrave (1690 or 1691 – 23 June 1766) was an Irish composer and organist.
He was born at Winchester but spent his early years in Dublin, studying music with his father, Daniel Roseingrave. In 1707 he entered Trinity College but failed to complete his degree. In 1710 he was sent to Italy with the financial assistance of St Patrick’s Cathedral, Dublin (awarded in 1709) in order "to improve himself in the art of music". In Venice he met Domenico Scarlatti and was greatly impressed by his harpsichord playing. He followed Scarlatti to Naples and Rome and, later in life, he published an edition of Scarlatti's sonatas for harpsichord which led to a "Scarlatti cult" in England.
Roseingrave composed several works in Italy including an anthem and a cantata. He returned to England in 1717 (having left Italy for Dublin in 1713) . In 1720 he produced Scarlatti's opera Amor d'un'ombra e gelosia d'un'aura under the title Narciso at the Haymarket Theatre, to which he added two arias and two duets of his own. He was appointed organist of St George's, Hanover Square, in 1725. He became known as an accomplished improviser, especially of fugues. He had a great admiration for the music of Palestrina and was highly skilled at contrapuntal writing. According to Charles Burney he could play the most difficult music by sight.