Obama bumped Chinese President Hu Jintao from the number one spot on the magazine’s annual rankings.
German Chancellor Angela Merkel remained the most powerful woman in fourth place, as Europe’s largest economy continued to wield its influence over the EU.
Russian prime minister Vladimir Putin, who is running again for president, was number two and Hu came third as he gradually manages the transition of power to others in China.
“The US remains, indisputably, the most powerful nation in the world, with the largest, most innovative economy and the deadliest military,” Forbes wrote.
Obama’s approval ratings have fallen at home as he struggles with stubbornly high unemployment and a tepid economy, but his fortunes on the world stage have been quite different.
Under orders from Obama, bin Laden, who helped orchestrate the September 11 attacks on the US, was tracked down in Pakistan and killed in May after 10 years in hiding.
The US joined the Nato-led intervention in Libya, which began with air strikes in March and led eventually to Gadaffi’s death in October.
Microsoft co-founder Bill Gates, at number five, was the first corporate executive on the list, thanks to a malaria vaccine backed by his charitable foundation that recently passed a key clinical trial.
Mark Zuckerberg, the 27-year-old head of social networking site Facebook, shot into ninth position from No 40 last year, sandwiched between US Federal Reserve Chairman Ben Bernanke (8), and British prime minister David Cameron at 10