The White House says Bush is expected to be on the ground in Iraq for more than five hours.
Bush has already met with Prime Minister Nuri al-Maliki in Baghdad's heavily fortified Green Zone. He is also due to see President Jalal Talabani.
Bush is to meet with Prime Minister Nuri al-Maliki and also with U.S. troops.
This is Bush's second visit to Iraq. He visited U.S. troops in November 2003.
Bush's visit comes just days after Abu Mus'ab al-Zarqawi, the Al-Qaeda leader in Iraq, was killed in an U.S. air strike.
(compiled from agency reports)