Juventus beat bottom side Crotone to go within eight points of leaders Inter Milan.
Ronaldo turned home an Alex Sandro cross before powering a header in from Aaron Ramsey’s ball, his 70th Serie A goal in just over two and a half years.
Crotone are the 78th team in Europe’s top five leagues to concede a league goal to Ronaldo.
Weston McKennie scored Juve’s third from close range.
Ronaldo is now Serie A’s top scorer this season, with 18 – overtaking Inter Milan’s Romelu Lukaku.
