Bachmann, 55, who came sixth with just five per cent of the votes, said during a news conference in Iowa that she has "decided to stand aside."
The Minnesota congresswoman, who had courted the evangelical Christian vote and was briefly the front-runner back in August, said she had "no regrets".
She did not endorse another candidate, but said that she "must rally around the person that our country and our party and our people select to be that standard bearer," The BBC reports.
Bachmann's exit leaves six Republicans in the race to challenge Barack Obama for the White House in November.
Mitt Romney, who narrowly won in Iowa, meanwhile rolled out an endorsement from ex-Republican nominee John McCain.
Rick Perry, who came fifth, vowed to press on, but will focus on the next-but-one race in South Carolina.
Romney is a heavy favourite to win next week's primary election in New Hampshire.
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