1647 Menelaus is a mid-sized Jupiter trojan from the Greek camp, approximately 42 kilometers in diameter. It was discovered on 23 June 1957 by American astronomer Seth Nicholson at the Palomar Observatory in California and later named after the Spartan King Menelaus from Greek mythology. The dark asteroid has a rotation period of 17.7 hours. It is the principal body of the proposed Menelaus cluster, which encompasses several, mostly tentative Jovian asteroid families.