Lazio claimed a Champions League place as Serie A leading scorer Ciro Immobile scored the winner when they came from behind to beat Cagliari 2-1 on Thursday and end a five-match winless run.
Giovanni Simeone gave Cagliari a halftime lead but Sergej Milinkovic-Savic equalised two minutes after the break and Immobile netted on the hour with his 31st goal of the season.
Lazio, fourth with 72 points, clinched the final Italian place in the Europe's elite club competition next season as they returned to the Champions League after a 13-year absence.
With three games left to play, Lazio still have a mathematical chance overhauling leaders Juventus, who lost 2-1 at Udinese earlier on Thursday and have 80 points.
"I'm happy, it's right to celebrate reaching an important target for us which we achieved three matches in advance," said Immobile.
"We are proud despite the difficulties we have faced after lockdown. This is something that Lazio haven't achieved for years."
Cagliari forward Joao Pedro scored with a stunning free kick early on but it was disallowed because the referee had signalled it was indirect.
Lazio were kept at bay by Cagliari goalkeeper Alessio Cragno and were caught out when Simeone gave the Sardinians the lead with a deflected shot at the end of the first half.
However, Milinkovic-Savic volleyed Lazio level two minutes after the break and, after hitting the post with a shot on the turn, Immobile latched on to Luis Alberto's through ball to slot the winner past Cragno on the hour.