Barack Obama made history when he was elected the United States' first African-American president in November 2008, and he swept to re-election with a victory over Republican Mitt Romney in 2012.
In a speech to supporters in Chicago after winning the election, Obama pledged to work with Democratic and Republican leaders to reduce the nation's federal deficit, fix the tax code, reform immigration and reduce the nation's dependence on foreign oil.
Obama's first term in office had been dominated by the passage of his Patient Protection and Affordable Care Act, colloquially known as "Obamacare", which he signed into law despite fierce Republican opposition.
Obama also ordered the bailout of the country's struggling car industry in 2009 and signed into law a repeal of the military's controversial "don't ask, don't tell" policy preventing gay people from serving.
He also signed into law the Dodd-Frank Wall Street Reform and Consumer Protection Act, which tightened regulation of the financial system.
On the international stage, Obama has withdrawn US troops from Iraq, a conflict he opposed from the beginning, although thousands of US troops remain in Afghanistan.
The president has failed to close the detention centre at Guantanamo Bay, as he had promised in 2008.
In 2011, the president ordered a team of Navy SEALs to kill Osama bin Laden, the leader of al-Qaeda, at his compound in Pakistan.
Beginnings
The son of a Kenyan father and US mother, Obama was born in Hawaii in 1961.