composer who was noted for his comic operas and who was instrumental in forming the Neapolitan (Neapolitan opera) style of opera composition.

Leo entered the Conservatorio della Pietà dei Turchini at Naples in 1709, where his earliest known work, a sacred drama, L'infedeltà Abbattuta, was performed by his fellow students in 1712. In 1714 he produced an opera, Il Pisistrato, for the court theatre. He later held various posts at the royal chapel and taught at the conservatory. His operas include La 'mpeca scoperta (1723), a comic opera in Neapolitan dialect; and Demofoonte (1735) and L'Olimpiade (1737), both serious operas. Leo is probably best remembered for the comic opera Amor vuol sofferenze (1739). His sacred works include six or seven oratorios, of which Santa Elena al Calvario (1732) was particularly esteemed; six masses; and a Miserere (1739) for double choir. He also wrote instrumental works, among them six concerti for cello and strings, organ fugues, and harpsichord toccatas. Leo's serious operas suffer from a coldness and severity of style, but in his comic operas he shows a keen sense of humour.