The Rocket dropped just seven frames all week as he set Alexandra Palace alight - playing some of the best snooker of his career, even leading Selby 8-1 at one stage.
O'Sullivan blitzed the first four frames, leading 4-0 after just an hour of play, before reeling off three of the next four to finish the first session 7-1 up.
Rocket Ronnie then claimed the opening frame of the evening session, although the Jester from Leicester hit back with two in a row to claw his way back to 8-3.
But O'Sullivan wasn't to be stopped as the reigning World Champion claimed the next frame before the mid-session interval and wrapped things up when the players returned to the arena - despite Selby first adding a fourth to his tally.
The win followed up victories over Robert Milkins, Ricky Walden and Stephen Maguire for the Rocket, as he lifted the fifth Masters title of his career in supreme style.
O'Sullivan told BBC Sport:
"I'm just pleased to have won. I don't know how I won it this week, to be fair. All wins are good but, coming into this week, I wasn't sure how I'd play. Sometimes the worst thing you can do against Mark is build up a lead! He's made of metal.
"I enjoyed it better watching it on the tele - it was hard work! I did miss playing and being amongst the lads. The crowd are brilliant here and they get involved and support all the players. We've had a fantastic atmosphere and I haven't got to drive so far in London!"
And Selby, who was playing in his fifth Masters final in seven years, said:
"Ronnie's fantastic at taking his chances. When he's in front, he seems to steamroll you. In the first session, he was very, very good. The damage was done in the first session really. You need to be on top of your game against Ronnie and I wasn't."
image: © dsykes34