A 20-year-old man hurled antisemitic insults at an elderly stranger, punching him in the face as he tried to enter a Brooklyn synagogue Monday night, police said.

The hate-fueled attack started around 9:30 p.m. in front of Congregation Kerem Shlomo on East 27th Street in Sheepshead Bay when the unhinged younger man suddenly socked the 67-year-old in the face and yelled antisemitic slurs, cops said.

“F—–g Jews!” he yelled, according to police sources. “I’m going to f–k you up. I see you Jews are racist.”

The alleged attacker, Hersham Ghonim, was arrested and charged with assault, assault as a hate crime, aggravated harassment, resisting arrest, criminal mischief and menacing, cops said. He was identified by police as black.

The NYPD Hate Crime Task Force was investigating, cops said.