Italian Sinner produced his best performance since returning from a three-month doping ban to thrash Casper Ruud 6-0 6-1.
The 23-year-old combined power with several deft touches to wrap up victory in one hour and three minutes.
Ruud arrived in Rome in fine form following his victory at the Madrid Open, but was unable to contend with the home favourite in the opening set.
The Norwegian world number seven fared slightly better in the second and was warmly applauded by the crowd after holding serve in the third game to end the onslaught.
But Sinner quickly regained his dominance and claimed the next four games to seal a 25th consecutive victory – a streak that was interrupted by the three-month suspension he agreed with the World Anti Doping Agency (Wada).
“I was feeling great on court today,” Sinner, who was playing in his fourth match since returning from suspension, told Sky Sports.
“My goal was to try to understand where my level is at this tournament and it has raised day by day.
“These are positive signs for me. Everything can change in one day but everything worked well for me. I was serving well and moved great on the court.”
Sinner is bidding to end a 49-year wait for an Italian winner of the men’s tournament in Rome, with Adriano Panatta the last home champion in 1976.
