Two goals from David Fuster and a late strike from Alan Pulido gave them a comfortable victory that puts them 21 points clear of second-placed AEK Athens, who only have seven games left to play and have a weaker head-to-head record.
Olympiacos have now won the title for six straight seasons and an astonishing 18 times from the last 20 campaigns.
It gives head coach Marco Silva, who has overseen 22 wins, one draw and one defeat from his team's 24 league games, a title in his first season at the helm.
Striker Konstantinos Fortounis has been crucial to his team's success, scoring 16 times to sit top of the league's goalscoring charts.