Voters in Houston have made history, electing the city's first openly gay mayor.

Houston mayor-elect Annise Parker, centre, smiles at her partner, Kathy Hubbard, left, as they celebrate Parker's election victory. (David J. Phillip/Associated Press)

Annise Parker seized 53.6 per cent of the vote in the hotly contested mayoral election Saturday.

Former city attorney Gene Locke conceded defeat after Parker built an unbeatable lead.

Of the more than 152,000 residents who turned out to cast ballots in the fourth-largest U.S. city Saturday, 81,652 chose Parker — some 11,000 votes more than were placed for Locke.

Parker said her administration will be about "transforming the lives of all Houstonians for the better."

Parker, 53, has been with her partner for 19 years and they have two adopted children.

She has never made a secret or an issue of her sexual orientation. But that orientation became the focus of the race after anti-gay activists and conservative religious groups endorsed Locke.

Locke, 61, tried to distance himself from the anti-gay attacks and condemned the divisive rhetoric. But two of his key supporters contributed money to a group that sent out an anti-gay mailer earlier this month, urging voters not to pick Parker because she was endorsed by the "gay and lesbian political caucus."