MILAN - I campioni d'Italia siamo noi! Inter win the 2006/07 Scudetto with a 2-1 victory over Siena as second-placed Roma went down by the same score against Atalanta.
Marco Materazzi gave Inter the lead, and scored again from the penalty spot after Negro's equaliser.
With 26 wins, 6 draws and just 1 defeat, Inter wrap up their second consecutive Serie A title with five games to spare.
Only two teams have managed that feat in Serie A history: Torino in 1947/48 and Fiorentina in 1955/56.
Materazzi got Inter off to a perfect start at the Franchi, firing in his seventh of the season from a yard out in the 18th minute after Negro's goalline block from Maicon's initial shot.
But the home side levelled against the run of play when ex-Lazio defender Negro headed in Rinaudo's headed assist from Galloppa's left-wing cross.
Manninger saved two powerful headers from Ibrahimovic as the Nerazzurri looked to increase their lead before the break.
If Inter needed a half-time tonic, it came from the Stadio Atleti Azzurri d'Italia as the news arrived that Atalanta had taken a 2-0 lead against Roma.
Relegation-threatened Siena almost edged in front right after the interval, but Julio Cesar made a crucial one-footed save from Negro's backheeled shot.
Inter got the goal they needed on 61 minutes when Materazzi surpassed his self-declared target of seven goals. The World Cup winner sent Manninger the wrong way with a spot-kick that had to be taken twice.
But Siena, still looking for their first ever home win against the Nerazzurri, weren't giving up and Inter had Maicon to thank for a goalline block from Galloppa.
On a hat-trick, Materazzi went close to increasing Inter's advantage but his far-post header from Recoba's pin-point delivery finished wide of the woodwork.
Zanetti made a headed clearance from Negro's flicked header, and Antonini crashed wide from close range as Siena launched a late assault on the Inter goal, but the Nerazzurri held on for the all-important victory.
Scudetto! Scudetto number 15. A title that will be dedicated to the unforgettable Giacinto Facchetti, who died just five days before the start of the 2006/07 championship.