He succeeds Louis Schweitzer, Renault boss since 1992, who now becomes non-executive chairman.
Ghosn told shareholders after the vote in Paris: "I am very happy to be back in France and to take charge of Renault. A new chapter of the group opens today. I arrived in Tokyo to lead a company in the midst of crisis. Renault is a healthy enterprise."
Ghosn takes Renault's leadership at a time when both companies are reporting a softening of their financial performance, partly as rising costs for steel and plastic trim profit.
Nissan Motor, which has leapfrogged Toyota Motor to number two spot in Japan since Ghosn took over, said on Monday that increased sales in the United States, its biggest market, of luxury vehicles like the Infiniti and Altima sedans, as well as a new offering of sport utility vehicles like the Pathfinder, helped push net income up 1.7% to a record $4.8 billion (£2.5 billion), beating the company's own forecasts.
But the gains in profit and sales were not as steep as they were for the past several years, and the company said it could only forecast a 1% gain in net profit for the year ending in March 2006.
Nissan Motor, 44% owned by Renault, also revealed it would need to postpone by one year a target to sell 4.2 million vehicles worldwide for the year ending in March 2009.
Ghosn said he would study the situation before taking action. His first visit will be to a Renault factory in France, followed by a trip to see operations in Britain.
"Do not expect large changes in the coming days," Ghosn said. "I first need to reconnect with a company that changed a lot since I left it."
Ghosn said he expected to push for a greater internationalization of Renault and an expansion of its product range.