The club have confirmed the official appointment of the eccentric Argentine after having said earlier this month they intented to appoint the former Athletic Bilbao coach.
Marseille hope that Bielsa will rediscover the magic enjoyed during Didier Deschamps' three-year reign.
Deschamps guided the 1993 European Cup winners to their first domestic league title in 18 years in 2010 but since his departure in 2012, OM have struggled to match up with the likes of Paris St Germain and Monaco.
Elie Baup and caretaker Jose Anigo were both let go after they failed to inspire the club's players.
Bielsa, who was in charge of Argentina from 1998-2004 and Athletic Bilbao from 2011-13, will take over from Anigo, who took over in a caretaking capacity last December.
Bielsa, 58, also coached Chile from 2007-11.
In 2012 he guided Athletic Bilbao to the finals of the Europa League and Copa Del Rey losing to Atletico Madrid and Barcelona respectively.
Marseille finished a disappointing sixth last season after being runners-up the previous year.
- Sports & Recreation
- Athletic Bilbao
- Didier Deschamps