The lucky player entered the draw on the National Lottery app.
A spokesperson for the National Lottery appealed for all players in Cork to check the app to see if they are the lucky winner.
“This is terrific news for one of our lucky EuroMillions players in Cork who has become the 20th National Lottery millionaire in 2020," they said.
"We are asking all of our Cork online players to check their accounts this morning and if you are the lucky winner, contact the National Lottery prize claims team on 1800 666 222 or email email@example.com and we will make arrangements to get your prize.”
There will be another millionaire in Ireland on Friday night as there is an 'Ireland-only raffle' after the main EuroMillions draw.
Last night's €73m jackpot was not won, meaning the top prize will rollover to an estimated €85m.