Giovanni Luigi Fieschi or Fiesco (c. 1522 – 2 January 1547) was a Genoese nobleman, count of Lavagna. He is the subject of the play Fiesco by Friedrich Schiller.
The Fieschi were one of the prominent families of Liguria, first mentioned in the 10th century. Among his kin were popes (Innocent IV and Adrian V), many cardinals, a king of Sicily, three saints, and many generals and admirals of Genoa and other states. He was extremely important to the Renaissance era.
Sinibaldo Fieschi, his father, had been a close friend of Andrea Doria, and had rendered many service to the Genoese republic. On his death in 1532, Giovanni found himself at the age of nine the head of the family and possessor of immense estates. He was described as handsome, intelligent, of attractive manners and very ambitious. He married Eleonora Cybò, marchioness of Massa, in 1540, described as a woman of great beauty and influence.
Giovanni Luigi Fieschi is best known for his part in a failed conspiracy against the Doria family. There were many reasons which inspired his hatred of the Doria family; the almost absolute power wielded by the aged admiral and the insolence of his nephew and heir Giannettino Doria, the commander of the galleys, were galling to him and many other Genoese. It is rumored that Giannettino had affairs with Fieschi's wife. Moreover, the Fieschi belonged to the French or popular party, while the Doria were aristocrats and Imperialists. Fieschi conspiracy against Doria found allies in Pope Paul III, in the Duke of Parma Pier Luigi Farnese and in Francis I of France. In Genoa, co-conspirators were his brothers Girolamo and Ottobuono, Verrina and R. Sacco.