Marseille parted company with Andre Villas Boas earlier this month after the Portuguese questioned the club’s transfer policy over the signing of Olivier Ntcham from Celtic in the winter transfer window.
Sampaoli left his role as manager of Brazilian side Atletico Mineiro earlier this week and heads to the Stade Velodrome, with Marseille performing well below their standards this season.
Marseille finished second on the Ligue 1 standings last season but are down in 7th place this term as they struggle to get among the European positions.
Sampaoli comes with a wealth of experience, having also managed Santos and Universidad de Chile. The 60-year-old led Chile to Copa America glory in 2015.
Marseille announced the arrival of Sampaoli alongside a message from owner Frank McCourt elevating sporting director Pablo Longoria to the position of club president.
"Frank McCourt announces profound changes, opening a new chapter for Olympique de Marseille," the club revealed in a statement published on Friday.
"Pablo Longoria is appointed president of the management board of Olympique de Marseille. Internationally renowned coach Jorge Sampaoli is appointed head of the first team."
Sampaoli added: “I've been told all my life that l'OM is a passion. Let the Orange Velodrome light up when the team goes to the stadium," the Argentine told Marseille's official website.
“Marseille is a people's club and I feel myself in this heat. We are not here to hide: we will play hard.
"When I received this proposal, I dreamed of being able to party in the city. In the world, there are quiet places and intense places. These are the ones I want and I accepted without hesitation. This club has a soul that's why we are here. We are ready. "
