The No.2-seeded Radwanska looked headed for another routine victory early on, storming out to a 5-2 lead in the first set, but in one fell swoop the No.7-seeded Halep won eight games in a row to go up 75 30 and take total control of the match, never really looking back en route to a 75 62 triumph.
"For sure the first set I should have won," Radwanska said. "I was 5-2 up. It was just one break, but that first set was mine. But she was playing really well today - everything was working for her.
"In some moments she was making unbelievable shots from nowhere from both sides and moving very well - at one point I didn't know what to do to finish the points, because she was just everywhere."
"It's been an unbelievable tournament for me," Halep said after the match. "I played really well tonight. When I was 5-2 down in the first set I told myself I have nothing to lose anymore, so I changed the tactics. I was still aggressive but played smarter - I started to play more crosses, more short crosses, and then I tried to finish the points with drive volleys. I also hit more drop shots as it went on too.
"I think I played a complete game tonight."
Afterwards, Halep told the crowd she hopes they come back to watch the final on Sunday.
"A lot of people came here tonight to support me, and every day too," Halep commented. "Every day they're coming and I like having all the support. My family and close friends are here as well.
"I just wanted to thank them for supporting me and that I want them to come tomorrow again."
Halep extended her winning streak against Top 10 players to five in a row - her last loss to a Top 10 player came against Serena Williams at Cincinnati last August. Also, her win over the World No.4 was the equal-best win of her career - she also defeated a No.4-ranked Radwanska at Rome last May.
And there's more - this isn't Halep's first Premier-level final, but none of her other Premier-level finals had more than an $800,000 total prize purse - the Qatar Total Open offers a $2,440,070 purse.
Awaiting Halep in the final is No.6 seed Angelique Kerber, who beat No.5 seed Jelena Jankovic in the first semifinal earlier in the day in a tight two-setter, 61 76(6) (read more about that match here).
Halep beat Kerber in the pair's only previous meeting, though it was five years ago at an ITF Women's Circuit event and 7-5 in the third set. As an indication of how insignificant that meeting might be, Kerber was ranked No.95 at the time and Halep No.228 - they are now No.9 and No.10, respectively.
"She's a great player, a top player," Halep said. "I have to start the match aggressively, and maybe if it's not working, I will change tactics again like I did today. But I still have to play my game."