HAMBURG — Mayor de Blasio — forgetting that he’s accountable to eight million Big Apple residents — blew off a Post reporter Saturday after he gave a speech in Hamburg, Germany.

The mayor did extensive interviews with German media after delivering a speech to activists protesting the gathering of world leaders at the G20 summit.

But when a reporter for The Post greeted de Blasio after he’d talked to the German reporters, he smiled, turned and walked away without any acknowledgment.

City Hall spokesman Eric Phillips said de Blasio appreciated the chance to spend time with his son and to meet with German protesters. The mayor will answer answer questions after returning to US soil.

“It’s been a good trip. We’ll be back in New York tomorrow,” Phillips said.

De Blasio and his aides were in Germany on the tab of Hamburg Zeigt Haltung – or Hamburg Shows Attitude.

The mayor’s son Dante joined the party in Hamburg. Dante de Blasio, a student at Yale, has an internship in Berlin this summer.

De Blasio flew to Hamburg on Thursday afternoon after skipping a somber NYPD swearing-in ceremony following the murder of officer Miosotis Familia.