The 57-year-old Spanish coach comes with a trophy-winning pedigree having led Valencia to the Copa del Rey title in 2018/19 and guided Athletic Bilbao to the Spanish Super Cup - their first trophy in 37 years - in 2021.
"Marcelino's arrival is in line with our desire to give continuity to the club's project. Our many discussions have shown a shared determination and understanding," Marseille's general manager of football Javier Ribalta said in a statement.
"His expertise and personality match the demands of the top level. His experience will also be a considerable asset in reinforcing the work undertaken last season."
Marseille will be Marcelino's first job outside Spain, having also coached Sevilla and Villarreal in a career spanning 27 years.
Former Croatia international Tudor signed a two-year contract in 2022 but left the French club earlier this month "for private and professional reasons" after leading them to a third-place finish in Ligue 1 last season.
