Top seed Azarenka of Belarus downed Poland’s world number four Radwanska 6-3 6-3 in their last-four clash.
Williams, seeded second at this tournament but back on top of the WTA rankings after reaching the semis, went one better with a 6-3 6-2 win over third seed Sharapova of Russia.
"Maria is always playing really well and so consistent, but I'm trying to be consistent as well," Williams 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, too."
It was the 10th time in a row the American has beaten Sharapova.
"When I go into a match, everything starts from scratch, even if I'm going against someone I've beaten many times," the Russian said.
"That's the way you have to look at every single match, no matter what your winning or losing record is against them. There's a reason why the nets go up in the morning.
"I'm certainly capable of beating a player like that, like Serena, no doubt - that's why I'm always eager to get better and make my game better in order to go out onto the court and beat her."
Azarenka's triumph was her seventh straight win against Pole Radwanska .
"I think it was a really high performance match from both of us," Azarenka said.
"It was a little bit shaky in the beginning - I think I did a little bit too many unforced errors and rushed a little bit into the rallies.
"But I started to be patient and more aggressive and dominant, really going for my shots when there was an opportunity, and taking advantage of every short ball she gave me. I'm glad I could turn it around."