Sylvio Lazzari (born Josef Fortunat Silvester Lazzari)[1] (Bolzano, December 30, 1857 - Suresnes, June 10, 1944) was a French composer of Austrian origin.
Lazzari came to Paris in 1882 after studying law in Austria. At the Paris Conservatory, he studied under Ernest Guiraud and Charles Gounod. Encouraged by Ernest Chausson and César Franck, Lazzari settled permanently in France and obtained French citizenship in 1896. He held several official positions in Paris, including president of the Wagner Society (from 1894) and choirmaster at the Opéra de Monte-Carlo.

Lazzari's use of cyclic structures was indebted to Franck; he was also heavily influenced by Wagner (especially in his operas) and the impressionists. Very few of his compositions have been performed since his death, but some of his chamber music is occasionally revived.