Cristiano Ronaldo watched on from the stands for Juventus, while Ciro Immobile clinched the Serie A Golden Boot and matched Gonzalo Higuain's all-time record on a busy Saturday night.
Napoli 3-1 Lazio
Napoli got back to winning ways in their last match of the campaign after seeing off Lazio 3-1 at Stadio San Paolo.
The hosts grabbed an early lead in the ninth minute after Fabian Ruiz drilled a strike from the edge of the box that took a deflection and left goalkeeper Thomas Strakosha stranded.
However, Lazio levelled matters in the 22nd minute after Ciro Immobie kept his composure to find the net with a right-footed shot inside the box to take his his tally to 36 league goals for the season.
Napoli were awarded a penalty nine minutes from the break after Marco Parolo brought down Dries Mertens inside the box, which saw Insigne convert with an unstoppable strike past Strakosha to restore the lead for the hosts.
Matteo Politano sealed the three points for Gattuso's men in stoppage time with a close range finish inside the box after receiving a through ball from Mertens.
Browse through the gallery to see the Serie A's top seven scorers this season.
Atalanta 0-2 Inter Milan
Inter Milan clinched second spot on the table after beating direct rivals Atalanta 2-0 at Stadio Atleti Azzurri d'Italia.
Antonio Conte's troops had a perfect start, as Danilo D'Ambrosio opened the scoring in just the first minute with a close- range header from a cross by Ashley Young.
Young doubled the lead for Inter in the 20th minute with a thumping strike from outside the box that hit the right post on its way to the back of the net.
There were no goals in the second stanza, as Inter held on to claim second spot on the log while Lazio finished third, four points behind Conte's charges.
AC Milan 3-0 Cagliari
AC Milan signed off the 2019/20 Serie A campaign on a high with a 3-0 victory over Cagliari at San Siro.
Milan got off to a dream start, as they went ahead in the tenth minute after Ragnar Klavan diverted Leao's shot into his own net.
The hosts had a brilliant chance to double their lead on the stroke of half-time after they were awarded a penalty for a handball inside the box, but Zlatan Ibrahimovic's spot-kick was saved by Cragno.
However, Ibrahimovic redeemed himself ten minutes after he break with an unstoppable strike after going one-on-one with Cragno.
Stefano Pioli's troops had their tails up as Castilejo gave added the third goal just before the hour-mark with a composed finish after rounding his marker inside the box.