Campaigners from across Europe will be meeting in central London on 19 May 2018, the day of the royal wedding, to discuss plans for a monarchy-free Europe.
The International Republican Convention is part of a four-day meeting of the Alliance of European Republican Movements (AERM). The UK's campaign Republic is hosting the event this year and will be welcoming guests from Sweden, Netherlands, Norway, Denmark and Spain. Speakers from the Commonwealth are also expected to be involved in the convention.
Graham Smith, CEO of Republic, which campaigns for an elected head of state, said: "Despite the fanfare and media hype, monarchies across Europe are facing an uncertain future. The age of deference is gone, scandals are more commonplace and demands for more democracy are stronger than ever."
"Here in the UK fewer than half 18-34 year olds support the monarchy, according to a recent YouGov poll. Most support for the royals is tied to the Queen personally, the prospect of Kings Charles will only make our job easier."
"In Britain the democratic crisis is more acute than it has been for decades. We have a creaking constitution that is not fit to deal with the huge challenges of the modern world."
"That's why I'm calling for a new constitution – one that's democratic top to bottom, one that rebalances power and gives us a useful, elected head of state."
Republic is a founding member of the Alliance of European Republican Movements, which was formed in 2010.
The AERM annual convention rotates around the member groups. Last year the event was in Sweden, next year it will be in Denmark. The last time the UK hosted the event was the weekend of the royal wedding in 2011.