Giulio Cesare Casseri (1552, Piacenza, Italy – 8 March 1616, Padua, Italy), also written as Giulio Casser, Iulius Casserius, Giulio Casserio, Giulio Casserio of Piacenza, was an Italian anatomist. Born in Piacenza, he moved to Padua as a young man, when he became a servant to the great anatomist Hieronymus Fabricius. Another of his teachers was Girolamo Mercuriale, who was Chair of Clinical Medicine in Padua from 1580-87. Casseri fell out with Fabricius, initially it seems as Fabricius resented the ethusiasm of the students for Casseri's teaching when Fabricius was ill.
He wrote Tabulae anatomicae, probably the most important anatomical treatise in the seventeenth century, published in Venice, in 1627. The book contained 97 copper-engraved pictures, by Francesco Valesio, inspired by Odiardo Fialetti, Italian painter and former student at Titian's school. The pictures in this book were copied in the works of his successor at Padua, Adriaan van den Spiegel (1578–1625). His De vocis auditusque organis historia anatomica was published in 1600-1 in Ferrara.