The Senegalese was president between 2005 and 2009 when Marseille finished second in Ligue 1 twice and reached two French Cup finals.
They went on to win a first French league title in 18 years in 2010.
"Pape will remain in the hearts of the Marseillais forever, as one of the great architects in the club's history," Marseille posted on Twitter.
The Ligue de Football Professionnel (LFP) said: "Journalist, agent, president of Olympique de Marseille, Pape Diouf dedicated his whole life in service of football.
"A member of the LFP administrative council from September 2007 to June 2009, Pape Diouf will be remembered as a charismatic and passionate director."
Former France and Liverpool striker Djibril Cisse played for Marseille when Diouf was in charge.
"Today French football has lost a great man," he posted on social media. "My sadness is great today. Rest in peace."
Manchester City's French defender Benjamin Mendy described his "sadness" at hearing the news.
"A great president but above all a huge man, who always worthily represented Marseille and its values. A great loss for French football and the African continent. Rest in peace," he tweeted.