The Fiat Yamaha rider came home backside Valentino Rossi and Andrea Dovizioso, but it was enough for him to secure the title with three races to go.
Reigning champion Rossi, who missed part of the season after breaking his leg at the Italian Grand Prix in June, started sixth, slipped down to 11th but worked his way back up and into the lead to receive his first win since the opening day of the season.
Rossi said he was "very happy" with his win and to end his barren streak, calling it "very important".
Going into the race, Lorenzo only needed to finish in the top ten to be crowned champion, which after season of almost back-to-back podiums including seven wins, always seemed likely.
With Rossi missing much of the season through injury, fellow Spaniard, Dani Pedrosa, has been Lorenzo's only serious rival for the title this season, but his hopes of snatching the title from Lorenzo evaporated last weekend when he broke his collarbone practising for the Japanese Grand Prix, putting him out of the races in Japan and Malaysia.
"Today is the happiest day in my life and we have to celebrate it," said Lorenzo, who held up a 'game over' signal at the end of the race.
"You always assume this second and dream in the region it but when it comes you don't know how to behave or what to say," He told us that.
"Jerez was the most special race victory of my life and since then - seven wins, only two races without a place on the podium - what greater can I ask for?".
Pedrosa, who is back in Spain recovering from surgery, also paid tribute to the new champion. "He rode very well this year correct from the beginning of the season and made very few mistakes - so he deserves the title," He told us that.