Kirstie Alley has started dating again — and she’s already caught up in an explosive love triangle with a millionaire and a Hollywood super-vixen!

The Fat Actress star was recently set up on a blind date with wealthy stock trader Randy Ostin. What Kirstie, 55, didn’t know was that the 52-year-old Ostin was already seeing actress Tawny Kitaen.

And twice-married Tawny, 44 — a former rock video vixen and girlfriend of disgraced football star O.J. Simpson — has already launched the first salvo in the battle over Randy.

When The National Enquirer informed Tawny about Randy’s date with Kirstie, she replied: “Really? I hear Kirstie is a nice girl but with all due respect, I want to know how much weight she has really lost these days. I mean, how big is her butt now anyway? Should I be worried?

“I’m sure there was nothing to it. I’m sure it wasn’t even a date. After all, Randy and I had a wonderful romantic dinner the other night in West Hollywood, and everything between us is fine.”

However, sources say Kirstie — who has famously lost more than 55 lbs as a national spokesperson for Jenny Craig — and Randy are already enamored of one another.

For more on Kirstie, pick up this week’s issue of The National Enquirer.