Ictinus (Greek: Ικτίνος, Iktinos) was an architect active in the mid 5th century BC. Ancient sources identify Ictinus and Callicrates as co-architects of the Parthenon.

Pausanias identifies Ictinus as architect of the Temple of Apollo at Bassae. That temple was Doric on the exterior, Ionic on the interior, and incorporated a Corinthian column, the earliest known, at the center rear of the cella. Sources also identify Ictinus as architect of the Telesterion at Eleusis, a gigantic hall used in the Eleusinian Mysteries.

The artist Jean Auguste Dominique Ingres painted a scene showing Ictinus together with the lyric poet Pindar. The painting is known as Pindar and Ictinus and is exhibited at the National Gallery, London.