Williams ensured she would become the oldest ever women's world number one, when the rankings are announced on Monday, by winning through to Saturday's semi-final against Maria Sharapova.
And the 31-year-old showed she is ready to remain at the top after almost two and a half years.
Williams needed just over an hour to dispatch the world number three 6-3 6-2 and set up a mouthwatering match with Azarenka on Sunday.
The Belorussian was similarly impressive as she brushed aside fourth-ranked Agnieszka Radwanska 6-3 6-3.
Azarenka is arguably in better form than Williams, after defending her Australian Open title last month. However, Williams will surpass her with fewer rankings points to defend.
Williams will beat the previous record set by Chris Evert, who was 30 years and 11 months when she was number one in November 1985.
The American has had to make her way back to the top after she missed almost an entire year on tour due to injury and illness in 2011, and briefly slipped as low as 175th in the world.
She cut her foot badly on glass in July 2010, and survived emergency surgery in Los Angeles in March 2011 - a haematoma and a pulmonary embolism having put her life in the balance - as she admitted at Wimbledon last year.
Azarenka praised Williams' achievement ahead of their clash on Sunday.
"She has really changed the women's game, really lifted it up," Azarenka told www.wtatennis.com.
"She's a legend in tennis. I don't know where I'm going to be at 31.
"It's definitely an incredible achievement."
Azarenka has won only one of 12 meetings against Williams but is determined to focus only on herself on Sunday.
"I just have to be consistent and really focused on my own game," she said.
"We all know she has a great serve. She's really aggressive and really consistent. So for me it's important to just focus on myself and execute my game. That's it."
Williams said she was looking forward to trying to win this tournament for the first time.
She said: "I love it here in Doha. I've never played this particular tournament but I've played in Doha before and had some good results, and I hope to have a good result in the final tomorrow [Sunday], too."