Gonzalo Higuain set a new Serie A record for goals in a single season by grabbing a hat-trick in Napoli's 4-0 win over 10-man Frosinone.
The Argentina international took his league tally for 2015-16 to 36, beating the previous record of 35 set by Gunnar Nordahl in 1950.
The win - helped by a red card for Mirko Gori prior to Marek Hamsik's opener - secured second place and Champions League group-stage football for Napoli, who managed to hold off a strong late challenge from Roma in the race to finish as runners-up.
Luciano Spalletti's side extended their superb run of form to finish the campaign with a 17-match unbeaten run as they cruised to a 3-1 win at AC Milan.
Mohamed Salah, Stephan El Shaarawy and substitute Emerson all scored for the visitors, who would have finished second had Napoli failed to beat Frosinone.
Carlos Bacca bagged Milan's late reply, his 18th goal of the season, but Cristian Brocchi's men must now beat Juventus in the Coppa Italia final if they are to secure a place in next season's Europa League.
Victory in that match would see them into Europe at the expense of Sassuolo, who impressively pipped Milan to sixth place as they rounded off a memorable season by beating Inter 3-1, Matteo Politano bagging two of the home side's goals.
Saturday's early kick-off, meanwhile, saw Juventus celebrate their fifth successive league title in style by crushing 10-man Sampdoria 5-0.
Paulo Dybala scored twice, with defenders Patrice Evra, Leonardo Bonucci and Giorgio Chiellini also finding the net as the Turin side chalked up their 29th win of the season to ensure they finish nine points clear of Napoli.