Ex-CEO Didier Lombard, along with six other former executives and the company itself, are accused of moral harassment in the first case of its kind on this scale in France, setting a potential precedent for large businesses.
The trial, in Paris' criminal court, is expected to run for the next two months.
Central to the case is a plan under which the telecoms operator, a former state monopoly, aimed to cut its workforce by 22,000 and redeploy 10,000 workers between 2006 and 2010. Prosecutors believe this plan triggered the wave of suicides.
Between April 2008 and June 2010, prosecutors listed 18 suicides and 13 suicide attempts by employees of Orange, still called France Telecom at the time, when the company was engaged in deep restructuring after its privatisation.
Lombard, who denied any wrongdoing, stepped down as CEO of Orange in early 2010 amid criticism of his handling of the crisis.
The former CEO and the other former executives risk two years in prison and a 30,000 euro (25,619 pounds) fine if found guilty.
An Orange spokesman declined to comment on the opening of the trial and the accusations but added that a lot of work had been done under current CEO Stephane Richard to improve the corporate culture.
The approach taken by former Orange bosses to accelerate cost-cutting plans had caused uproar in France.
"I'll get them (the employees) out one way or another, through the window or the door," Lombard told a gathering of France Telecom's senior executives on Oct. 20, 2006, according to notes from the meeting that later came to light.
According to union records, the suicide wave claimed the lives of over 30 workers in two years, including a man who stabbed himself in the stomach during a staff meeting and a woman who threw herself out of a window.
A 2010 report by labour inspectors said management used "pathogenic" restructuring methods such as forcing people into new jobs and giving them unattainable performance objectives.
These conclusions were followed up by public prosecutors in their own investigation.
They stressed that Orange executives wanted to unsettle employees by deliberately making their work disorganised and forcing them to move from one place to the other. They also denounced the use of excessive and intrusive control methods including threats.
The reorganisation took place against the backdrop of the deregulation of the telecommunications sector and the gradual privatisation of France's incumbent operator.
(Reporting by Emmanuel Jarry and Mathieu Rosemain; Writing by Mathieu Rosemain; Editing by Keith Weir)
By Emmanuel Jarry and Mathieu Rosemain