It'll end with a five-part story, which will include the return of Faith, the bad-girl slayer, and Buffy's first love, Angel.
"We're gearing up to tell a fabulous, huge, great arc. It's going to be pretty spectacular," said Sarah.
Sarah Michelle Gellar in Scooby Doo
The mastermind behind the series, creator Joss Whedon has also admitted it's ending.
He said: "Well, it's hard to think at all, or stand, or form vowel sounds, so maybe it's time to take a break," he added.
"I'm just glad I can say we did our best on every single episode. We didn't always succeed, but we never slacked, and I'm immensely proud of my writers, actors and crew for that."
But as we told you recently, there may be a spin-off series starring Faith.
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