Lastheneia (or Lasthenia) of Mantinea (Greek: Λασθένεια Μαντινική) was one of Plato's female students.

She was born in Mantinea, an ancient city in Arcadia, in the Peloponnese. She studied in the Academy of Plato dressed as a man.^[1] After the death of Plato she continued her studies with Speusippus, Plato's nephew.^[2] She is also said to have had a relationship with Speusippus.^[3]

A papyrus fragment from Oxyrhynchus mentions an unidentified woman who studied under Plato, Speusippus, and then Menedemus of Eretria.^[4] The fragment goes on to explain that "in her teens she was lovely and full of unstudied grace." This woman is probably Lastheneia or Axiothea of Phlius.