Ciro Immobile scored in Lazio's final game of the season to match Argentina forward Gonzalo Higuain's record of 36 goals, set while playing for Napoli in the 2015-16 season.
It was Juventus's second consecutive defeat since sealing a ninth Serie A title in a row, just days before their Champions League campaign resumes against Lyon.
From Lionel Messi, to Cristiano Ronaldo, Mohamed Salah, Robert Lewandowski and Erling Braut Haaland, nobody in Europe has managed to keep pace with Lazio's Ciro Immobile.
A win would pull Lazio within five points of Juventus, but a defeat in Turin would see them fall 11 points off the pace with four games to play.
Lazio consolidated second position, behind the eight-time Serie A reigning champions Juventus, who had dominated Lecce 4-0 in Turin on Friday.
Serie A: Lazio vs Napoli match seemed headed for a goalless draw but all that changed with eight minutes remaining.
Italy's fourth win in five games leaves Gian Piero Ventura's men second in Group G, on the same points as leaders Spain, who beat Israel 4-1.