The King will host French President Emmanuel Macron and his wife this summer on their first state visit to the UK.
Buckingham Palace announced the president has accepted the King's invitation and will visit from 8-10 July.
Mr Macron and his wife, Brigitte Macron, will stay at Windsor Castle.
Foreign Secretary David Lammy said a UK-France summit will happen during their visit "to grow our economies, safeguard borders and bolster our security".
State visits are grand ceremonial affairs and usually include a carriage ride and a lavish state banquet.
It will be the first state visit of a French president since March 2008, when Nicolas Sarkozy was invited by the late Queen. He also stayed at Windsor Castle.
The Macrons hosted King Charles and Queen Camilla on a state visit to France in September 2023.
It was meant to be his first state visit as monarch but was postponed due to protests, and he visited Germany, then Romania, ahead of France.
The King and Queen were also hosted by Mr Macron in June 2024 when they attended events to mark the 80th anniversary of D-Day in Normandy, but that was not a state visit.
The following month, Charles was seen greeting the French president at the European Political Community meeting at Blenheim Palace in Oxfordshire.
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Charles, 78, was diagnosed with cancer early last year and has been continuing his duties while undergoing treatment.
The King is due to host US President Donald Trump after Sir Keir Starmer gave him an invite in February, but a date for the trip has not yet been announced.
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