Two Uber France executives could face jail in a case hinging on the taxi company's banned low-cost service.
The trial of Thibaud Simphal and Pierre-Dimitri Gore-Coty comes a week after France's top constitutional authority upheld a 2014 law outlawing the low-cost UberPop service, which allowed any driver to act as a taxi. Uber's standard app-based service remains legal in France.
The two men face up to two years in prison and fines of 300,000 euros (£222,400).
Uber is under increasing pressure to work with sceptical European governments. It is banned entirely in Spain and Italy, but French politicians say they understand the demand for such services.
During protests in France this summer, taxi drivers infuriated by Uber competition smashed livery cars and set tyres on fire.