The fine, the biggest the regulator has ever slapped on an individual company, comes after competitors Bouygues Telecom and SFR complained that Orange had been hindering free competition in the business market for fixed and mobile phones since the early 2000s, the authority said.
Bouygues has since dropped out of proceedings after reportedly receiving a large payoff from Orange.
Orange had established a number of anti-competition practices, especially loyalty schemes, that stopped corporates from picking a different operator for even part of their telecoms needs, the authority said.
The competition authority said it had ordered Orange, which had been cooperating in the investigation, to immediately re-establish a "healthy competition situation" in its markets.