The Lisbon side, who collected a fifth title in six years, finished two points above nearest challengers and historic rivals FC Porto, who came from behind to win 2-1 at home to Sporting as both sides had a player sent off.
Top scorer Haris Seferovic sent Benfica on their way in front of a packed and noisy Stadium of Light with a cool finish in the 16th minute and teenage midfielder Joao Felix slammed the ball into the roof of the net soon after.
Benfica deny reports of Diego Costa agreement
Forward Rafa Silva increased Benfica's advantage before the interval and Seferovic struck a fourth in the 56th minute, although defender Cesar Martins soon pulled one back for the visitors.
Porto had to beat third-placed Sporting and hope for a favour from Santa Clara to retain the title but they fell behind to a strike from Luiz Phellype just after the hour mark despite the visitors having Cristian Borja sent off in the 19th minute.
Midfielder Danilo Pereira levelled for Porto in the 78th and Hector Herrera grabbed a late winner but the victory mattered little as Benfica finished the season on 87 points to Porto's 85.
Bow down and recognise the brilliance of Bukayo Saka - The Warm-Up
Arsenal comeback an 'example for the future', says Aubameyang