As much as the score made the match seem a completely one-sided affair, Azarenka actually had multiple chances to get ahead before Williams served out the match to love after one hour and 34 minutes.
Williams adds the Italian Open title to her wins in Miami, Charleston and Madrid and heads in to Roland Garros on a career-best 24 match unbeaten streak.
The victory in Rome is Williams’s second Italian Open triumph, her first coming in 2004 when she also picked her only French Open title to date.
"It wasn't easy, nothing is ever easy," Williams said. "Last year I was feeling excellent on clay but didn't do that great at Roland Garros; this year I'm cautious and I want to work hard and stay focused and win every point I play, and not slack at all."
Williams admitted that she would, however, allow herself one deviation from her usually strict training diet - an Italian ice cream. "This is what I was waiting for," she said. "I'll have pistachio - it's the only one I get."
Azarenka made a bright start to the match as she raced out to a 40-0 lead before being pegged back and broken by Williams in an opening game that lasted more than eight minutes.
The Belarusian had immediate chances to break back but could not take advantage and quickly found herself two breaks down after again failing to take her chances to hold in the third game.
Although Azarenka did finally get on the scoreboard in the fourth game, getting one of the breaks back after a very poor drop shot attempt from the world number one, the Belarusian was left to rue missed opportunities. She was 3-1 down when she could just as easily have been 3-1 up.
Having given herself a stern talking to in between games, Williams immediately re-established her double break lead, harnessing her anger into a series of brutal forehands which left Azarenka reeling.
The world number one quickly held to go 5-1 ahead before breaking for a fourth time to seal what looked like a comfortable opening set but which in reality had taken 46 tough minutes and the determination to save multiple break points.
The second set quickly looked like it was going to follow the same path before Azarenka finally managed to secure a hold of serve in the second game, being forced to save yet more break points before holding with a huge first serve.
Another service hold followed for Azarenka in the fourth game of the set, the Belarusian again saving break points before managing to hold when Williams pulled a forehand wide across court.
The American finally did break in the sixth game, Azarenka going wide with a forehand, only to hand the Belarusian the immediate break back with a poor game that concluded with a forehand into the net from Williams.
But Williams was not going to let an increasingly positive Azarenka force her way back into the match and broke again in the eighth game, a double fault from the Belarusian seeing her concede her serve.
The world number one had no trouble in backing up the break this time, serving out the match without the loss of a point and securing victory with consecutive aces and a forehand winner down the line.