In Greek mythology, Polydora was the daughter of the hero Peleus and Antigone, the daughter of King Eurytion of Phthia, making her a member of the Aeacid line and a sister or half-sister of Achilles. She married Borus, the son of Perieres of Messenia, who wooed her with a large dowry, yet she became the mother of Menesthius by the river-god Spercheius. "Polydora" was a name borne by several distinct figures in Greek mythology, and the sources preserve more than one account of who Menesthius's mother was.
Adapted from Wikipedia, "Polydora" · CC BY-SA 4.0
I.Daughter of Peleus
Polydora was the daughter of Peleus and Antigone, the daughter of King Eurytion of Phthia, which places her within the Aeacid line and makes her a sister (or half-sister) of Achilles. Her father Peleus had been purified by Eurytion and married Antigone in Phthia before later accidentally killing Eurytion during the hunt for the Calydonian boar.
She married Borus, the son of Perieres of Messenia, who wooed her with a large dowry. Despite this marriage, Polydora became the mother of Menesthius by the river-god Spercheius. In Homer's account, Menesthius is one of the leaders of Achilles' Myrmidons, born to a daughter of Peleus and reckoned as the offspring of Spercheius though nominally the son of Borus.
II.Daughter of Perieres
A separate tradition names a different Polydora as the daughter of Perieres and as the wife of Peleus. In some accounts she, rather than Peleus's daughter, became the mother of Menesthius by Spercheius.
This variant reflects the confusion among the ancient sources over the parentage of Menesthius's mother: in one branch she is Peleus's daughter who marries into the house of Perieres, and in another she is herself a child of Perieres who marries Peleus.
III.Other figures named Polydora
The name Polydora belonged to several other characters in Greek mythology. One was the Oceanid Polydora, called the "handsome," one of the three thousand water-nymph daughters of the Titans Oceanus and his sister-spouse Tethys.
Another was a Danaïd, a daughter of King Danaus, who was said to be the mother of King Dryops of Oeta by the river-gods Spercheius or Peneus. A Polydora of Messenia was the wife of Aphareus and thus the possible mother of his children Idas, Lynceus, and Peisus.
A further Polydora was the daughter of Meleager and Cleopatra; married to Protesilaus, she was so overcome with grief at his death that she took her own life. One of the Amazons also bore the name Polydora.
IV.Sources
The figures named Polydora are attested across the major ancient authors. Homer's Iliad records Polydora the daughter of Peleus as the mother of Menesthius, while Apollodorus' Library, Hesiod's Theogony, Pausanias' Description of Greece, Theocritus' Idylls, and Antoninus Liberalis' Metamorphoses preserve the other figures and the variant genealogies.
Because Wikipedia treats "Polydora" as a set of distinct mythological figures, the daughter of Peleus is documented chiefly through her appearance in the Homeric catalogue of the Myrmidons and through the parallel accounts of Menesthius's parentage.