After almost 19 years together, Maria Menounos and Keven Undergaro are ready to tie the knot! Undergaro popped the question with a special on-air proposal Wednesday morning for the world to hear.

While on Howard Stern's SiriusXM show to promote her new book "The EveryGirl's Guide to Cooking," the 37-year-old "E! News" host was hit with quite the surprise from her longtime boyfriend. It all seemed innocent when Stern asked her if she ever wanted to date anyone else, but little did Menounos know that was Undergaro's hint to come on set.

"At the end of the day, Keven and I are partners in life," she told Stern. Undergaro then came in and Stern wasted no time asking her why she hadn't pressured him to propose after 19 years together.

"Howard, I'm the one who's telling him now, 'We have to do this,'" she explained. "He's like, 'No! I want a big affair. Kris Jenner says she's going to be the godmother and throw the big party.'"

Undergaro was then handed the microphone, and Menounos got suspicious. "Are you about to propose to me? I'm going to die," she said. "Oh my God, it felt like he was about to propose right now." And then he took her completely by surprise.

"Although I said that this isn't a proposal, I want to ask you something," he said said while getting down on one knee. "Will you make me the happiest man on earth?"

Menounos was taken aback by the question as she responded saying, "Are you friggin' kidding me right now? Is this a joke?"

"It's not a joke," he explained. "This I wouldn't joke about. I love you so much and this show's meant so much to both of us...Why not make it official now? Will you honey? Will you accept?"

Only Stern, his wife Beth and Undergaro's mother and Menounos' father knew that this was about to happen, and Menounos obviously said yes. "Yes, yes, yes! Oh, my gosh! Of course!" she excitedly replied. "I can't believe this is happening."

As someone who has been a regular guest on Stern's show since she first appeared in 2004, the host was pleased with how things went. "After 19 years, it's about f--king time with you two," he told the happy couple.

The ring, which Robin Quivers described as "big" on the show, is a custom ring designed by French jeweler Jean Dousset. The jewelry designer and Undergaro worked together to create this "one of a kind" ring, which has 220 intricately set brilliant-cut diamonds, just for Menounos.

"I am truly flattered to create this ring, 19 years in the making," Dousset said. "Keven chose to add personal elements to the ring by including a Signature Stone hidden underneath. The choice of color and origin of the stone adds thoughtful detail only he and Maria will know and see."

Listen to the full proposal below!