The 13th seed, who first won the event in 2012, beat her American opponent to love in the opening game and never looked back on her way to a straight-sets 6-4, 6-4 victory. 

Two-time champion Williams conceded the first set in 41 minutes after failing to convert her five break chances in the sixth and eighth games.  

Her troubles deepened when she dropped her first service game of the second, then failed to take any of four break points in the next game to trail 2-0.

Despite dropping her serve again, Williams roared back in the eighth game to convert her first break point at the 10th attempt for 5-3 before holding serve to increase the pressure on Azarenka.

But it proved to be too little too late for the 21-time Grand Slam champion as Azarenka thwarted two break point opportunities at 5-4 before clinching the win after 88 minutes.

"Well, I [had] to go for it," said Azarenka.

"She's not a type of player that if you are going to play safe, she's going to give [you the point] or she's going to miss.

"You really have to go out there and take away, because there is nothing coming easy."

Victory for the two-time Australian Open champion earned her a 19th Women’s Tennis Association (WTA) Tour title and sees her move back into the top 10 of the world rankings as of tomorrow.  

It is only the fourth time the 26-year-old has beaten Williams in 21 meetings and the first since the 2013 Cincinnati Masters final.

Williams had not featured in the final at the Indian Wells Tennis Garden since 2001, having begun a 14-year boycott of the tournament after she was booed, along with father Richard, due to her sister Venus controversially withdrawing.

"The last moment I had here wasn't so great," Williams told the crowd.

"Thank you so much.

"The cheers...I can't begin to tell you how much it means to me."

In the men's final, world number one Novak Djokovic beat Canada’s Milos Raonic 6-2, 6-0 to claim his 27th Masters title and draw level with Spain's Rafael Nadal for the most wins. 

The 28-year-old Serb was barely tested by his opponent who was forced to take a seven-minute injury break between sets due to a lower back injury that affected his serve.

Djokovic made just four unforced errors to Raonic’s 27 en route to securing the 62nd title of his career in one hour and 17 minutes.

"I think it is the best I played all week," said Djokovic, who now has five Indian Wells titles to his name.

"Milos' injury allowed me to move him around the baseline, his first serve problems allowed me to step in and dictate the play, and I was on top of his every second serve."

In a news conference prior to today’s matches, tournament chief executive Raymond Moore caused controversy when he claimed the WTA "ride on the coat-tails of the men".

"If I was a lady player, I'd go down every night on my knees and thank God that Roger Federer and Rafa Nadal were born, because they have carried this sport," said Moore.

"They really have."

Williams reacted angrily to Moore's "offensive" statement, for which he later apologised, branding the remarks "mistaken and very, very, very inaccurate".

"If I could tell you every day how many people say they don't watch tennis unless they're watching myself or my sister, I couldn't even bring up that number," she added.