Tudose handed in his resignation on Monday evening after senior members of the ruling Social Democrats (PSD) voted to withdraw their support at a leadership meeting.
“I am leaving with my head held high. I’m going to get my things at parliament,” Tudose told journalists after the party gathering.
The move heralds fresh turmoil for Romania, one of the European Union’s poorest countries plagued with corruption scandals, and comes on the eve of a historic visit by Japanese Prime Minister Shinzo Abe.
Tudose’s resignation will have to be signed off by centre-right President Klaus Iohannis. He also needs to approve the PSD’s new prime ministerial nominee, to be chosen at a party meeting on Tuesday.