The Kildare native scooped up the award for his role as Stanley Kowalski in the brand new London production of Tennesse Williams' A Streetcar Named Desired.
Having been staged at the Amedia Theatre in North London, the play was transferred to West End stage, the Phoenix Theatre in March, with Mescal receiving rave reviews for his performance.
Accepting the award at the Royal Albert Hall, Paul Mescal thanked his mother Dearbhla who is being treated for cancer, saying that "I hope you get better".
It was a very successful night for the new production of the classic play, as Mescal's co star Anjana Vasan also won an Olivier Award for Supporting Actress on the night.
Having previously won IFTA and BAFTA awards for his breakout role in Normal People back in 2020, Paul Mescal was also nominated for an Academy Award for his role in Aftersun this year.
Fans will be able to watch Mescal currently star in psyhological drama God's Creatures, alongside Emily Watson.