Obama edges out President Donald Trump, 17 per cent to 14 per cent, while former secretary of state Clinton moved past Michelle Obama, 9 per cent to 7 per cent and First lady Melania Trump scored one per cent, the poll said.
Obama wins over Trump, who is suffering brutally low approval ratings as he is about to complete his first year in the White House. He came in second place followed by Pope Francis.
Trump's approval rating sank to a new low in CNN polling in December, earning the approval of just 35 per cent of Americans less than a year into his first term.
The former president has made it to the top of the list for the past 10 years, while the former presidential candidate has won 16 years in a row.
Gallup said sitting presidents usually win the most admired spot, and that Obama was the first former president to top the list since second world war general and post-war president Dwight Eisenhower.
"The incumbent president is the usual winner, since he is arguably the most prominent figure in the country," Gallup said in a statement. "But when the president is unpopular, other well-known and well-liked men have been able to finish first."
Gallup notes that this poll has been administered 71 times since 1946 and the incumbent president has won 58 of those times and Clinton has held the title 22 times in total, more than anyone else.
Results are based on telephone interviews conducted with a random sample of 1,049 adults, ages 18 and older, living in all 50 US states and the District of Columbia.