The French subsidiary of Ikea will go on trial on Monday over allegations that it snooped on employees and customers by using private detectives and police officers.
Ikea France will be tried as a corporate entity alongside several of its former executives.
Prosecutors say Ikea France set up a "spying system" across its operations.
The 15 people in the dock include top executives such as former CEO Stefan Vanoverbeke, and former store managers.
Four police officers are also on trial for handing over confidential information.
Ikea has already fired four executives over the scandal and put in place a new code of conduct. However, the company still faces a fine of up to €3.75 million ($4.5 million).
The allegations first came to light in 2012 after an Ikea insider leaked emails between the company and a security company to the satirical newspaper Le Canard Enchaîné.
The emails suggested that the firm was seeking access to records about its staff and customers from a police database holding millions of names and the personal information of criminals, victims and even witnesses.
Two unions filed complaints against Ikea, accusing the company of spying on hundreds of employees and customers.
The court is investigating the period between 2009 and 2012, but prosecutors say practices in France started nearly a decade earlier.
Jean-Francois Paris, Ikea France's former director of risk management, is accused of sending lists of names to be investigated to private investigators. The bill for these investigations could have been up to €600,000, according to court documents seen by the AFP news agency.
Mr Paris has said his department was responsible for handling the payments for investigations.
One staff member "who used to be a model employee, but has suddenly become a protester" was investigated over concerns they could become "a risk of eco-terrorism", according to emails sent by Mr Paris.
The charges against the defendants include illegal gathering of personal information, receiving illegally gathered personal information, and violating professional confidentiality. The charges carry prison terms of up to 10 years.