Guglielmo della Porta was an Italian architect and sculptor of the late Renaissance or Mannerist period.
He was born to a prominent North Italian family of masons, sculptors and architects. His father Giovanni Battista della Porta was a sculptor. He trained in his uncle's workshop in Genoa and moved to Rome about 1537, where he was very much influenced by Michelangelo. Della Porta provided legs for the Farnese Hercules when it was first excavated; when the original legs were found some years later, Michelangelo recommended that Della Porta's legs be retained, as showing how modern artists were capable of direct comparison with the Ancients. He was appointed to the papal mint in 1547. His prolific output is varied. He began his artistic training under the guidance of his uncle Giovanni Giacomo, who takes him on his construction site of the Cathedral of Milan and assigned him the task of sculpturing and reinterpreting the works of Leonardo da Vinci until about 1530. Later he moved with his uncle in Genoa where he perfected his design under the guidance of the painter Perin del Vaga in the works for Villa del Principe, Palazzo di Andrea Doria.