Sammartini, Giovanni Battista (jōvän`nē bät-tēs`tä säm-märtē`nē), c.1701–75, Italian composer. Sammartini lived most of his life in Milan. He was influential in the development of the Classical style of Haydn and others. Stylistically advanced, he contributed to the growth of classical form, especially of the symphony. Gluck studied with him. Sammartini's brother Giuseppe (1695–1750) was also a composer.