Ripoll previously served as assistant to Christian Gourcuff, who left his position at the end of the season following 11 years in charge at the Stade du Moustoir.
President Loic Fery believes the appointment will provide stability for Lorient.
Speaking to the club's official website, Fery said: "The appointment of Sylvain Ripoll is consistent with the philosophy of Lorient and its development policy.
"He is imbued with the values of Lorient and is a fan of good football, with a fighting spirit.
"I considered his sense of community and his ability to sustain a philosophy of play while providing his personal touch. This appointment is a continuity in the identity of Lorient."
Ripoll, who featured in more than 200 games for Lorient before sustaining a serious knee ligament injury that curtailed his playing career, is relishing the new challenge.
"I am very excited about this new (opportunity) and fully honoured by the trust placed in me," he said.
"I am determined to meet this challenge to build a magnificent adventure. I want to meet this challenge to bring the club on even further."
