Ryan Sweeting and Kaley Cuoco are engaged! Credit: Dan MacMedan/WireImage.com

Kaley Cuoco is gearing up for another big bang: A wedding! After a whirlwind three-month courtship, the Big Bang Theory star, 27, is engaged to tennis star Ryan Sweeting, her rep confirms exclusively to Us Weekly. "It's only been three months but she knows Ryan is the one," a source close to the actress explains. "When you know, you know."

Sweeting, 26, proposed on Wednesday, Sept. 25 -- just a few days after the couple made their red carpet debut together over the weekend at a pre-Emmys bash and then at the Emmy Awards show itself in L.A. The CBS star was accordingly in a joyful mood on social media after accepting the proposal. "Flying high, I could literally touch the sky with you . . . " she tweeted to her 1.6 million followers. On her Instagram account, she shared a snapshot with her best friend Ashley and sister Briana . "A sweet celebration w my sweet soul sisters," the caption wrote.

Another telling Instagram snapshot depicted two adorable penguins walking side-by-side. "I love u @ryansweething :)" she cooed to her man.

It will be the first marriage for both, who first stepped out together at a horse ranch in Moorpark, Calif., in early August.

Adds the pal: "[She's] never felt this way. She knows this is it. And the ring is gorgeous!"