Carles Puigdemont, who led Catalonia's bid for independence from Spain, is expected to gather thousands of supporters on Saturday in the French southern city of Perpignan, just 30 kilometres from the Franco-Catalan border.
It is the first time the former leader of Catalonia has been on the outskirts of Spain since fleeing more than two years ago.
Puigdemont left after declaring independence from the rest of Spain following a referendum that Madrid considered illegal.
He was pursued by Spanish authorities for alleged rebellion in relation to the push for Catalonia to split from Madrid.
It's the first time Puigdemont has risked going to France, where police and the courts work closely with Madrid.
He was boosted recently after winning a legal battle that grants him immunity from prosecution because he is an MEP.
"For me, it's like being at home," said Puigdemont to the daily La Dépêche du Midi on Wednesday.
Attending a rugby match on Friday, he proudly wore the gold and red colours around his neck.
The organisers have reserved 600 buses and estimate that between 70,000 and 100,000 separatist activists will make the trip from Spain for this rally.
The meeting is set to start at noon CET in Perpignan's Exhibition Park, despite the COVID-19 coronavirus outbreak.
“It is surreal what is happening in Perpignan," said François Meylan, president of Catalunya Peuple d'Espagne, which opposes independence. "Since the first cases of coronavirus appeared in Europe, different countries are taking action.
"In Switzerland, they have just banned all acts that house more than 1,000 people. Not cancelling this event is a danger to public health.”
A sensitive context
The rally has been heavily criticised, especially by former French Prime minister and unsuccessful candidate for mayor of Barcelona, Manuel Valls.
"Elected officials of all stripes will receive with great fanfare in Perpignan a political leader who has fled Spain and who is being sued by the justice of a state governed by the rule of law. This separatist who has nothing progressive about him says he comes to 'Catalonia-north' and not to France." he tweeted.
Puigdemont's meeting takes place in a sensitive political context in Catalonia.
Some early regional elections have been announced in January due to tensions between the two ruling separatist parties, Puigdemont's Together with Catalonia and Oriol Junqueras's Left Republican of Catalonia, Puigdemont's former number two.
The first party advocates disobedience whereas the latter is more favourable to dialogue with Pedro Sanchez' socialist government in Madrid.