Italian violinist and composer, one of the first great violinists who practiced virtuosity for virtuosity's sake, thereby extending the technical vocabulary of the violin. He is perhaps best known for his L'Arte del violino, a group of 12 violin concerti issued with 24 capriccios ad libitum for solo violin.

At age 14 Locatelli was a member of the instrumental ensemble of Santa Maria Maggiore in Bergamo. At 16 he went to Rome, perhaps to study with violinist-composer Arcangelo Corelli (Corelli, Arcangelo), though he may well have studied with a number of other eminent musicians in and around the city at that time. Locatelli toured widely, refining his skills. Ultimately, about 1729, he settled in Amsterdam, where he gave up public performance in favour of regular concerts for a group of wealthy amateurs. There, too, within the strong Dutch music publishing tradition, he published his works. His playing was particularly admired for its double stops (playing two strings at once), and he frequently used special tunings for special effects. Some of the bravura passages in his studies and caprices, which anticipate those of Niccolo Paganini (Paganini, Niccolò) in their concentration on technical feats, slight the musical content for the technical effect. As a composer, Locatelli was most drawn to the sonata and concerto forms. Both reveal him to have been capable of elegant and expressive melody.