The Brazilian attacker struck twice in four second-half minutes at the Estadio da Luz to propel Jorge Jesus' quadruple-chasers seven points clear with just two rounds remaining
The Estadio da Luz was growing increasingly restless as the Eagles struggled to break down their stubborn opponents - despite dominating both possession and territory.
However, Lima broke Olhanense's resistance just before the hour-mark and struck again just four minutes late to seal Benfica's 33rd Primeira Liga title.
The Eagles had gone into the weekend seven points clear of second-placed Sporting, who cut the gap with a win over Belenenses on Saturday night.
That left Jorge Jesus' men knowing that nothing other than victory against Olhanense would clinch the title with two rounds remaining.
Consequently, the Benfica boss ignored the temptation to rest some star men ahead of Thursday's Europa League semi-final first-leg clash with Juventus and named a strong starting line-up.
He was perhaps made to regret that decision, though, after Toto Salvio was forced off with an apparently serious arm injury, with Lazar Markovic coming on in the in-form winger's place for the start of the second half.
Benfica became increasingly desperate the longer the game wore on but their incessant pressure finally told in the 57th minute when Lima was on hand to convert after Olhanense goalkeeper Vid Belec failed to hold a Nicolas Gaitan strike.
The pressure lifted, and Olhanense's resistance belatedly broken, Lima struck again moments later, albeit once again with the help of Belec, who inexplicably allowed the Benfica striker's shot from out wide to squirm under his body.
The nature of the goal mattered not a jot to the home fans, of course, as it kept their beloved Benfica on course for a remarkable quadruple, with Juve to come in the Europa League, and final dates already booked for both the Taca de Portugal and Taca da Liga.
Before all that, though, the Eagles took time out to celebrate their first Primeira Liga success in three years and, in the process, pay tribute to club legend Eusebio, who sadly passed earlier this year.
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