Ictinus (active second half of 5th century B.C.) was a Greek architect and the chief designer of the Parthenon. In addition, he is known to have prepared a design for the Telesterion, the great hall of the Mysteries at Eleusis.

Of what city Ictinus was a citizen is not known, but the importance of the building projects assigned to him in Athens makes it not unlikely that he was an Athenian. Like Phidias, he may have been part of a coterie of artists and intellectuals who were particularly favored by Pericles and who were assigned the task of formulating and giving external expression to the ideals of Periclean Athens.

The intellectual side of Ictinus's activity is confirmed by Vitruvius, who records the existence of a treatise about the Parthenon written by the architect and an associate named Carpion. This treatise presumably dealt with the well-known "refinements" of...