In remarks at Arlington National Cemetery near Washington, Obama paid tribute to US military personnel who served in conflicts such as World War Two as well as the more recent wars in Iraq and Afghanistan, which he wound down as commander in chief.
"For many of us, this Memorial Day is especially meaningful. It is the first since our war in Afghanistan came to an end," Obama said. "Today is the first Memorial Day in 14 years that the United States is not engaged in a major ground war."
As a Democratic presidential candidate in 2008, Obama sharply criticized the war in Iraq.
US forces are now involved in air campaigns against Islamic State militants in Iraq and Syria as well as training missions in Iraq and Afghanistan. The president has been reluctant to relaunch ground operations in Iraq.