Johann Jakob Greber (? – buried 5 July 1731) was a German Baroque composer and musician. His first name sometimes appeared in its Italianized version, Giacomo, especially during the years he spent in London (1702 – 1705). Greber composed solo cantatas, sonatas, and stage works, including the opera Gli amori di Ergasto which opened London's Queen's Theatre in 1705. He died in Mannheim, where for many years he was Kapellmeister of the court orchestra of Charles III Philip, Elector Palatine.