Mescal's Connell was never seen without the chain in the BBC adaptation of Sally Rooney's novel, and it even inspired fans to launch an Instagram page.
The actor gave co-star Daisy Edgar-Jones one of his chains as a wrap gift but he kept another and last month, he agreed to sell it to help raise funds for Pieta House.
"Thank you so much to everyone who participated... 70,340 euro is a huge amount of money and will go a long way in supporting Pieta's vital services," Mescal tweeted after learning the chain had been won.
"Thank you to everyone who entered & for all the generous donations for the raffle of @mescal_paul 's chain. We have been blown away by the global support," a statement from the charity reads.
The lucky winner, Eadaoin Regan, also received a congratulatory tweet from Paul.
Mescal raffled off the chain after revealing Pieta is a cause "very close to my heart", revealing he "experienced loss due to suicide in my local town while growing up".
He added that the series touches upon depression and suicide, adding, "It seemed like a very special partnership to want to help those in similar situations."