Coordinates: 36°41′09″N 27°22′30″E / 36.68583°N 27.375°E / 36.68583; 27.375

Knidos or Cnidus ( /ˈnaɪdəs/; Ancient Greek: Κνίδος [knidos]) is an ancient settlement located in Turkey. It was an ancient Greek city of Caria, part of the Dorian Hexapolis. It was situated on the Datça peninsula, which forms the southern side of the Sinus Ceramicus, now known as Gulf of Gökova. By the fourth century BC, Knidos was located at the site of modern Tekir, opposite Triopion Island. But earlier, it was probably at the site of modern Datça (at the half-way point of the peninsula).

It was built partly on the mainland and partly on the Island of Triopion or Cape Krio. The debate about it being an island or cape is caused by the fact that in ancient times it was connected to the mainland by a causeway and bridge. Today the connection is formed by a narrow sandy isthmus. By means of the causeway the channel between island and mainland was formed into two harbours, of which the larger, or southern, was further enclosed by two strongly built moles that are still in good part entire.