Speaking at the White House, Obama said "in Germany I'll visit with Chancellor Merkel who's probably been my closest international partner these last eight years."
Obama is set to arrive in Germany on Wednesday, touching down at Berlin's Tegel airport, before meeting the German Chancellor.
He will also meet there with French President Francois Hollande, British Prime Minister Theresa May and Italian Prime Minister Matteo Renzi.
The leaders plan to discuss the crises in Syria and Ukraine, as well as the fight against the Isis terror group.
In a pre-trip news conference, Obama told reporters he would "signal our solidarity with our closest allies and express our support for a strong, integrated and united Europe."
"It's essential to our national security and it's essential to global stability," he said.
"That's why the trans-Atlantic alliance and the NATO alliance have endured for decades under Democratic and Republican administrations," he added, seeking to allay fears that Trump will try to sideline the alliance.
Obama also said he believes his successor has a "commitment to NATO."
During his time in office, Obama has often singled out Merkel for special attention among his European allies.
In 2011, Obama honoured the Chancellor by awarding her the Presidential Medal of Freedom, praising her “eloquent voice for human rights and dignity worldwide.”
In April, Obama praised Merkel for her “courageous” leadership during the ongoing refugee crisis, a sentiment he has often repeated.