And he's carrying some heavy burdens.
There's the threat from Islamic State militants in Iraq and Syria, and the Syrian civil war and refugee crisis. Also, Russia's moves in Ukraine and, more recently, in Syria.
On Monday evening, Obama and Russian President Vladimir Putin (POO'-tihn) meet on the sidelines of the U.N. gathering. It will be their first face-to-face encounter in nearly a year.
Obama wants to focus on Ukraine. Putin wants to talk about Syria.
Obama is scheduled to address world leaders earlier Monday.