Rwandan genocide suspect Félicien Kabuga was arrested on Saturday in the Paris region, said the French Ministry of Justice.
Kabuga, 84, who lived under a false identity in an apartment in Asnières-sur-Seine, near Paris, has been prosecuted by international justice for 25 years, the ministry said in a statement.
French gendarmes arrested him at 05:30 GMT on Saturday, the ministry said.
Kabuga is the most wanted man in Rwanda and the United States has put a bonus of $ 5 million on his head.
A Hutu businessman, he is accused of having financed the militias which massacred some 800,000 Tutsis and moderate Hutus over a period of 100 days in 1994.