The Dijlah - the name for the Tigris River in Arabic - was inaugurated in the southern port city of Basra, officials said.
The 14,000-ton capacity, Chinese-built ship will help ease export problems Iraq has encountered as its beleaguered but vital oil industry begins to recover from years of war and neglect, officials said.
Basra Gov. Mohammed al-Waili led the ceremony and said the Dijlah would help spur growth in Iraq's oil industry.
Iraq's fleet of oil tankers was battered by the 1980-88 Iran-Iraq war and then by the first Gulf War.