Napoli have won their first Scudetto since 1990 after Victor Osimhen's second-half goal secured a 1-1 draw at Udinese on Thursday night.
They came within six minutes of securing the title on Sunday, but drew with Salernitana, meaning that Lazio had a mathematical chance to overtake the runaway leaders. That chance has now disappeared.
Sandi Lovrić's clinical finish from inside the penalty area on 13 minutes rocked Luciano Spalletti's side, who struggled to create chances at the other end, although Osimhen threatened with a couple of first-half headers.
But when the Nigerian striker pounced 12 minutes after half-time, calmly side-footing in a rebound, it sparked celebrations among thousands of travelling Napoli supporters, and the tens of thousands at Diego Armando Maradona Stadium in Naples, where the match was shown on big screens.
Napoli have led the table for most of the season, producing the best and most entertaining football by some distance, spearheaded by Osimhen and the Georgia winger Khvicha Kvaratskhelia. They have lost three league games all season.
They also looked on course to go far in the Champions League before a surprise 2-1 aggregate defeat against Milan at the quarter-final stage.
Victor Osimhen's 22nd goal of the season ensured Napoli secured the single point needed to clinch the title with rivals Lazio and Juventus no longer able to catch them.
Udinese had threatened to spoil the party for the thousands of travelling Napoli fans when Sandi Lovric put the home side ahead after 13 minutes.
But after Osimhen's equaliser Napoli held on to finally end their 33-year wait for the Scudetto and spark a wild party on the streets of southern Italy.