Obama topped the annual list for the sixth consecutive year, a typical ranking for a sitting U.S. president, the polling organization said.
But the percentage of those surveyed who choose him as the most admired man fell to 16 percent this year, down from 30 percent in 2012.
The president's job approval rating has dropped during a year marked by a botched healthcare rollout and stalled legislative initiatives at the start of his second term.
Clinton earned the top spot among most admired women for the 12th consecutive year and 18th time overall, more than any other woman in the poll's history.
Fifteen percent of Americans surveyed gave the former first lady and U.S. senator the highest ranking, down from 21 percent who named her as the most admired woman last year, the poll showed.
Gallup said its data came from a poll of 1,031 adults between Dec. 5 and 8, and had a margin of error of plus or minus 4 percentage points.
Other men named to the list included former U.S. presidents George W. Bush, Bill Clinton and Jimmy Carter; Pope Francis and the Reverend Billy Graham; actor and director Clint Eastwood; Microsoft Corp co-founder and philanthropist Bill Gates; U.S. Senator Ted Cruz of Texas and former Republican presidential candidates Mitt Romney and Ron Paul.
The women who finished behind Hillary Clinton included talk show host Oprah Winfrey, first lady Michelle Obama, former Alaska Governor Sarah Palin, former Secretary of State Condoleezza Rice and actress Angelina Jolie.
Also on the list were Malala Yousafzai, the Pakistani teenager shot in the head by the Taliban for demanding education for girls; German Chancellor Angela Merkel, and Britain's Queen Elizabeth and Duchess of Cambridge, Kate Middleton.