Menestheus (Greek: Μενεσθεύς), the son of Peteus, son of Orneus, son of Erechtheus, and either Polyxene or Mnesimache, was a legendary King of Athens during the Trojan War. He was set up as king by the Dioscuri when Theseus travelled to the underworld, and at his return Menestheus exiled him from the city.

Menestheus was one of the suitors of Helen of Troy, and when the Trojan War started he brought "fifty black ships" to Troy. In the Iliad it is noted that no one could arrange chariots and shield-bearing warriors in battle orders better than Menestheus, and that only Nestor could vie with him in that respect. Yet further he is characterized as not valiant. When Agamemnon was reviewing his troops he found Menestheus in the back rows seemingly avoiding action. Later when Sarpedon attacked the portion of the Greek wall that he was in charge of, Menestheus shivered and had to call on Telamonian Aias and Teucer for aid. Menestheus was one of the warriors in the Trojan Horse. After Troy was sacked, he sailed to Mimas, then to Melos where he became king.