Giovanni Battista Fontana was an Italian composer and violinist of the Baroque period.
He was born in Brescia, and worked there and in Rome and Padova. He died in Padova during a plague.
Nearly all information preserved about him comes from the preface of his posthumously published 18 (sometimes incorrectly stated 12) sonatas (Sonate a 1.2.3. per il violino, o cornetto, fagotto, chitarone, violoncino o simile altro istromento, Venice, 1641). They are among the earliest sonatas of this form, consisting of 6 sonatas for solo violin/cornetto with continuo and 12 sonatas for one to three violins and continuo, the latter group often including a demanding concertante part for bassoon or cello. An "atto di morte" dated 7 September 1630 for a “Zan Batta Fontana” aged 50, is the only one among the Paduan death registers of 1625–30 for a person bearing that name.