The 30-year-old Brazilian, a little-known journeyman until he joined Benfica two years ago, broke the deadlock in the 57th minute and added a second goal three minutes later helped by a blunder from goalkeeper Vid Belec.
Benfica’s 11th successive league win gave them an unassailable seven-point lead over second-placed Sporting with two games to play.
Although Benfica are Portugal’s most successful club with a record 33 league titles, they have spent most of the last two decades in the shadows of arch-rivals Porto.
Coach Jorge Jesus had to watch from the stands as he was suspended following his sending-off in the Cup semi-final against Porto on Wednesday.
“It was very complicated,” the 59-year-old, who was also in charge for the 2010 title-winning campaign, told reporters.
“You feel like you’ve lost your power. You want to correct mistakes and there’s nothing you can do. It made me very anxious.”
“This was the culmination of hard work by a lot of people who believed it was possible. It was our big target,” he added.
Benfica, looking decidedly jittery, missed a flurry of early chances.
Rodrigo side-footed weakly at Belec when he seemed certain to score in the sixth minute and squandered another chance four minutes later when he fired wildly over from an excellent position.
Olhanense grew in confidence and held out until Belec only partially stopped Nicolas Gaitan’s low shot and Lima snapped up the rebound.
Three minutes later Lima burst down the right and a seemingly harmless shot squirmed through Belec’s legs for his 14th goal of the championship.
“It’s the high point of my career,” said Lima, who has never played for Brazil and is at the 12th club of his much-travelled career.
Sporting, who won 1-0 at Belenenses on Saturday, are guaranteed second spot and a place in the Champions League group stage next season.
Porto, champions 14 times in the last 20 seasons, need to beat Rio Ave on Monday to make sure of third position and a slot in the Champions League qualifying rounds next season.
(Reporting by Brian Homewood, editing by Ed Osmond)