He was born in Bergamo in Italy. He studied in Rome and settled in Amsterdam in 1729, where he died.
Locatelli's works are mainly for the violin, an instrument on which he was a virtuoso. His most significant publication is probably the Arte del violino, opus 3, a collection of twelve concertos for the instrument which incorporate twenty four technically demanding capriccios (or caprices) - these could function as extended cadenzas, but are now usually extracted and played in isolation from the concertos.
Locatelli also wrote violin sonatas, trio sonatas, concerti grossi and a set of flute sonatas (his opus 2). His early works show the influence of Arcangelo Corelli, while later pieces are closer to Antonio Vivaldi in style.
Locatelli may be best known to the modern public for a piece that does not actually exist. Master and Commander, the first novel in Patrick O'Brian's Aubrey-Maturin series, begins with the famous line: 'The music-room in the governor's house at Port Mahon, a tall, handsome, pillared octagon, was filled with the triumphant first movement of Locatelli's C major quartet.' In fact, Locatelli is not known to have written any quartets.