Senegalese defender Kalidou Koulibaly's stunning last-gasp goal kept Napoli's title hopes alive with a 1-0 win at Juventus closing the gap to just one point on the Serie A champions.
Koulibaly headed in the winner off a Jose Callejon corner in the final minute to give Napoli their first ever victory at the Allianz Stadium.
Six-time defending champions Juventus's lead at the top of the table has been cut to just one point with four games left. It was just their third league defeat this season and a first since November 19.
Juventus have 85 points from 34 games with Napoli, bidding for a third Scudetto after 1987 and 1990.
Maurizio Sarri's side pushed forward and had numerous chances, while Juventus, apart from a Miralem Pjanic free-kick hitting the post, created little.
Napoli captain Marek Hamsik threatened twice to break the deadlock while Lorenzo Insigne had a goal disallowed for offside in the first half, before substitute Piotr Zielinski's late snapshot was cleared by Gianluigi Buffon.
"It was not the perfect match but it was a great match: we did not concede anything to Juventus and the victory was a logical consequence of this attitude," said Sarri.
The champions now have a difficult run-in to the season, including trips to Inter Milan and Roma -- both fighting for Champions League places.
Napoli will play Fiorentina, Sampdoria, Torino and Crotone in their final four matches.
"We're still top of the table, we still have the advantage. There are four games to go, two at home and two away, so we'll see what happens," said Juve boss Massimiliano Allegri.
Elsewhere, Lazio and Inter kept their push for Champions League football alive on Sunday.
Ciro Immobile scored a brace as Lazio crushed Sampdoria 4-0 to stay fourth, just behind Roma.
Inter are a point further back in fifth, just outside the Champions League places, after a hard-fought 2-1 win over Chievo.
