EU trade commissioner Phil Hogan is to resign.
He said he deeply regretted his trip to Ireland caused such “concern, unease and upset”.
He has been under intense pressure after attending an Irish parliamentary golf society dinner in the west of Ireland last week with 80 other people in the midst of the coronavirus pandemic.
He said: “This evening I have tendered my resignation as EU trade commissioner to the President of the European Commission, Dr Ursula von der Leyen.
“It was becoming increasingly clear that the controversy concerning my recent visit to Ireland was becoming a distraction from my work as an EU commissioner and would undermine my work in the key months ahead.”
Mr Hogan had been expected to play a key role in establishing the EU’s relationship with Britain following Brexit.
He travelled around Ireland during his summer break from Brussels despite official rules stating he should have self-isolated for 14 days because of the rate of infection abroad.
Ms von der Leyen had sought an explanation from her commissioner amid disquiet from the highest levels of the Irish Government.
Mr Hogan was among 81 guests who attended a controversial golf dinner in Clifden in the west of Ireland last week.
He said: “I have always tried to comply with all relevant Covid-19 regulations in Ireland and had understood that I had met with all relevant public health guidelines, particularly following confirmation of a negative Covid-19 test.
“I reiterate my heartfelt apology to the Irish people for the mistakes I made during my visit.”
That event attracted widespread anger since it came a short time after Ireland tightened its restrictions on the number who can meet amid a rising number of coronavirus cases.
Large social gatherings are discouraged to hamper spread of the virus.
The commissioner held significant standing in Brussels after a stint as agriculture commissioner and a long career as a Fine Gael politician.
He was recently involved in negotiating a limited trade deal with the US around tariff reductions.
The Irish Government has said Mr Hogan breached its public health guidelines.