Haris Seferovic opened the scoring in the 16th minute, volleying in from Andreas Samaris's lofted pass behind the defence, and highly-rated youngster Joao Felix made it 2-0 soon after, showing great composure to evade a tackle and smash in from close range.
Rafa Silva got in on the act late in the half, burying a rebound, before Seferovic wrapped up the win with another smart volleyed finish, this time via Alex Grimaldo's cross.
Victory sees Benfica finish the campaign two points better off than second-placed Porto, which defeated Sporting CP at the Dragao.
Benfica did not always look destined for the title, however, as Bruno Lage took charge in January with the Eagles fourth in the table and seven points adrift of Porto.
Since then, Benfica has won 17 of its 18 league games, losing none, highlighting the incredible improvement inspired by the 43-year-old coach.