Denmark PM Mette Frederiksen is said to have been left shocked and suffering whiplash after being struck by a man while walking in the centre of Copenhagen.
The assault took place in a square in the city's old town when a man walked up to the politician and hit her.
The attacker was swiftly arrested, but there is no word yet on a motive.
European Commission chief Ursula von der Leyen called it a "despicable act, which goes against everything we believe in and fight for in Europe".
The attack on another European leader comes less than a month after Slovak PM Robert Fico was shot several times as he greeted supporters. He survived and has since undergone surgery.
Two witnesses - Marie Adrian and Anna Ravn - described the Copenhagen assault to the local newspaper BT, saying: "A man came by in the opposite direction and gave her a hard shove on the shoulder, causing her to fall to the side."
They said that while it was a "strong push" the prime minister did not hit the ground and that she sat down at a nearby café to recover.
Mette Frederiksen's office said that the incident had left the politician "shocked" and that she was suffering "minor whiplash".
A 39-year-old man is due to appear at a hearing at the Frederiksberg Courthouse on Saturday afternoon in connection with the incident.
The attack comes two days before Denmark votes in the EU election.
Ms Frederiksen, leader of Denmark's Social Democrats, had earlier taken part in a European election event with her party's lead candidate Christel Schaldemose.
The Social Democrats are the biggest party in Denmark's coalition government. They still lead the polls, but their support has fallen back considerably in recent months.
Danish Environment Minister Magnus Heunicke said on X: "Mette is naturally shocked by the attack. I must say that it shakes all of us who are close to her."
EU chief Charles Michel said on X that he was "outraged".
"I strongly condemn this cowardly act of aggression," he said.
Ms Frederiksen, 46, became prime minister in 2019 after taking over as leader of the centre-left Social Democrats four years earlier. This made her the youngest prime minister in Danish history.
Soon after, she became embroiled in a spat with then-President Donald Trump after she rebuffed his idea of the US buying Greenland.
Mr Trump called her "nasty" after she dismissed the suggestion of such a land deal as "absurd".
In 2022, Ms Frederiksen was heavily criticised by a commission investigating her government's decision to cull millions of mink during the Covid pandemic.
