Antonio Conte's side have not tasted defeat in Serie A since a 4-2 defeat at Fiorentina in October, but that record was in doubt at the Stadio Olimpico as the visitors played over an hour with 10 men.
Lazio have not beaten Juventus in the league since December 2003, but they were given a huge boost when the visitors' goalkeeper and captain Gianluigi Buffon was shown a straight red card for bringing down Miroslav Klose in the area.
Antonio Candreva held his nerve to score the resulting penalty, sending replacement goalkeeper Marco Storari the wrong way in the 27th minute.
Juventus did not appear to be hindered by the dismissal, however, and they continued to dominate the tempo.
The reigning champions were rewarded on the hour mark when a superb move was finished by Fernando Llorente's looping header from Stephan Lichtsteiner's pin-point cross.
Earlier on Saturday, Napoli's fading title hopes suffered another blow with a disappointing 1-1 draw against strugglers Chievo at Stadio San Paolo.
The visitors took a surprise lead after 18 minutes via a superb driven half-volley from Gennaro Sardo.
Rafael Benitez's men should have equalised in the 25th minute when Jose Callejon's ball across the face of goal was inexplicably put wide by Gonzalo Higuain at the back post with the goal gaping.
Dries Mertens also went close when his effort from an acute angle struck the outside of the post.
It looked like Napoli were heading for defeat, but their relentless pressure finally told in the 88th minute when Raul Albiol drove a half-volley into the floor that bounced into the bottom corner.
The result means that Napoli remain third and 12 points behind leaders Juventus, while Chievo are just one point above the relegation zone in 16th.
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