Son of Azzolino II, marquess of Fosdinovo and nephew of Spinetta Il Grande, Galeotto and his brother  inherited their uncle's fief, as he died without any descendants. He lived in Verona, where he studied law. He eventually became an eminent judge of the City and married the noble Genoese Argentina Grimaldi.

He was the first marquess to settle at Fosdinovo, acquired a few years earlier by his uncle Spinetta. Erected in 1367, his monument is located in Saint Remy church at Fosdinovo. It depicts Saint John, Saint Peter and Paul, then again Saint John introducing the knight to Jesus and the Virgin.