The marine was killed on Saturday in an explosion while on combat duty in the city of Haditha, a statement from Camp Falluja said.
As of Saturday 2 April 2005, at least 1533 members of the US military have died since the beginning of the Iraq war in March 2003, an Associated Press count said.
Meanwhile, a huge explosion rocked the vicinity of Iraq's foreign ministry, shooting a cloud of smoke into the sky, shortly after parliament elected a speaker on Sunday, an AFP reporter said.
No further details were immediately available on the blast which struck just before 2pm (1000 GMT).
The foreign ministry is located in central Baghdad, not far from the Green Zone, the sealed off enclave which is home to parliament and the US embassy. Fighters had fired mortars into the Green Zone during the parliament's previous two sessions.