Taoiseach Micheál Martin has spoken by phone today with Britain's new Prime Minister Liz Truss.
A Government statement said: "The Taoiseach extended his sincere condolences to the UK government, King Charles III and the royal family, and the British people on the loss of Her Majesty Queen Elizabeth.
"They reflected on her historic State visit to Ireland in 2011 and its contribution to advancing reconciliation and relations on these islands."
The Taoiseach also "offered his congratulations to the Prime Minister on her appointment, and told how he looked forward to working constructively with her".
Mr Martin and Ms Truss also discussed the "illegal Russian invasion of Ukraine, their support for Ukraine, and recognised the substantive EU-UK cooperation as part of the global response".
They exchanged views on "common challenges including soaring energy prices and the rising cost of living" as well as the Northern Ireland Protocol.
The two leaders have agreed to keep in close contact in the coming weeks.
