Mnestheus (Ancient Greek: Μνησθεός) is a character from Roman mythology, found in Virgil's Aeneid. He is described by Virgil as the ancestral hero of the Memmii and "Of the house of Assaracus". One of a handful of vaguely defined lieutenants under Aeneas, he appears to be Aeneas's most senior captain, taking charge in Book 9 in his absence. He takes second place in the boat race during the funeral games of Anchises in Book 5.

• 9023 Mnesthus, Jovian asteroid named after Mnestheus
• Mnestheus (skipper), a genus of butterflies

• Virgil IV, 288; IX, 171, 781.
• A Dictionary of Greek and Roman Antiquities edited by William Smith (1870).

• Virgil. The Aeneid (in English) at Project Gutenberg