Giovanni Battista Benaschi, or Beinaschi, (1636–1688) was an Italian painter and engraver active in the Mannerist style.
He was born in Turin. He first trained in the Piedmont, under a painter by the name of Spirito, then was the main pupil of Pietro dal Po in Rome. As was customary, his master had Benaschi draw from the Carracci frescoes from the Farnese Gallery, from the statues in the Belvedere at the Vatican Palace, paintings from San Carlo de' Catinari and the works of Lanfranco from the church of Sant Andrea della Valle. Among his patrons were Giovanni Battista Cesalassi and the Jurist Alberettti. In Naples, he painted several ceilings and frescoes, for example at the Chiesa di Santa Maria in Portico, and the cupula of Santi Apostoli. He completed an etching of a Holy Family, after Giovanni Domenico Cerrini, who was his intimate friend.
Benaschi died in Rome. His sister, Angela Beinaschi, was a portrait painter. Among his pupils was Orazio Frezza.