The Vermont legislature overturned the governor's veto and legalized same-sex marriage on Tuesday.
The state Senate voted 23-5 to override Gov. Jim Douglas' veto and the House voted 100-49 to override.
Douglas had vetoed the bill on Monday, saying the state's civil union law is sufficient in extending the same rights and benefits of marriage to same-sex couples and that he believes marriage should remain between a man and woman.
Vermont was the first in the country to enact civil unions for same-sex couples nine years ago.
The New England state is now the fourth state to allow gay and lesbian couples to marry. It is also the first to legalize same-sex marriage with a legislature's vote.
The gay marriage affirming vote comes on the heels of a ruling by the Iowa Supreme Court last week that also opened the door to same-sex couples marrying.
The court ruled last Friday that the 1998 Defense of Marriage Act, which limited marriage to a man and a woman, was unconstitutional.
Same-sex marriage is also legal in Massachusetts and Connecticut.