Varadkar is now tipped to beat housing minister Simon Coveney to become the country's next Taoiseach - what the Prime Minister is called in Ireland. But that's not Varadkar's only first - he'll also be Ireland's youngest prime minister ever at 38 years old.
"If my election shows anything it's that prejudice has no hold in this Republic", Varadkar said.
Ahead of the 2015 vote on a referendum legalizing gay marriage, Varadkar, then a cabinet minister, came out as gay.
Ireland's governing Fine Gael party is counting ballots in a leadership election that will determine the country's likely next prime minister.
Speaking after the result was announced, Varadkar said he was delighted, humbled and honoured to win.
"He's a once-in-a-generation politician", said Fine Gael member of parliament Jim Daly, echoing the comments of most of his colleagues who have placed high hopes in Varadkar.
He was a practising doctor before joining politics and being elected in 2007.
Ireland's new Taoiseach is not expected to be formally confirmed until 13 June when the Dail parliament resumes. On the other hand, in 2015, it became the first nation to agree and allow on gay marriage after voting on it.
"We are happy that he is a member of our family who is going to script history and become the world's youngest prime minister".
Mr Kenny congratulated Mr Varadkar last night and also paid tribute to Mr Coveney, a TD for Cork.
He will succeed Enda Kenny as leader of the centre-right party within weeks.
"It is not something that defines me". "It's not something that defines me", he said.