Madeline Miller has won the Orange Prize for Fiction with her debut novel The Song of Achilles.
The classics teacher-turned-novelist picked up the STG30,000 ($A48,000) prize at a central London ceremony on Wednesday night.
Chair of the judges Joanna Trollope said her retelling of the ancient Greek myth was "relevant and contemporary".
Ms Trollope said: "This is a more than worthy winner - original, passionate, inventive and uplifting. Homer would be proud of her."
The novel retells the story of Patroclus and the legendary warrior Achilles from their first meeting as children to their deaths at the siege of Troy.
Novelist Kate Mosse, who co-founded the prize, said it was "a wonderful novel".
She said: "It is a story about difference, about myth, about telling the story people think they know and adding imagination to it".
Ms Miller, who lives in New England, spent 10 years writing the novel while working as a Greek and Latin teacher.
She beat former winner Ann Patchett, Dubliner Anne Enright, Esi Edugyan, Cynthia Ozick and Londoner Georgina Harding to the prize.
Jonathan Ruppin, from booksellers Foyles, described her as a "dark horse" winner.
He said: "Word-of-mouth has been spreading steadily for this stylishly told and fascinatingly detailed story of classical-era same-sex romance involving literature's ultimate flawed hero."
Past winners of the prize, given to the best novel of the year written in English by a woman, include Tea Obreht, Zadie Smith and Linda Grant.