Ukrainian comedian Volodymyr Zelensky won a landslide victory in the presidential election.
Mr Zelensky had taken over 73% with President Petro Poroshenko receiving only 24%.
"I will never let you down," Mr Zelensky told supporters.
Mr Zelensky, age 41, is known for starring in a comedic television series "Servant of the People", where his character accidentally becomes Ukrainian president.
He is also an Instagram star with 4.2m followers. Zelensky, is a millionaire and owns a production company called Kvartal 95. He studied Law in University.
It will be about a month before the inauguration. President Poroshenko, has been in power since 2014. Poroshenko explained, "I will leave office but I want to firmly stress - I will not quit politics."
Edited and shortened from BBC