The shocking announcement -- as many fans were expecting fan-favorite Luke Pell to be the next Bachelor -- was made during ABC's Bachelor in Paradise: After Paradise on Tuesday night.
After Paradise host Michelle Collins and co-host Sean Lowe introduced the new Bachelor and Viall walked out onto the set. Screams and loud applause could be heard from the audience.
"I'm very excited but I'm more nervous. I'm very excited," Viall said on the after show.
Bachelor in Paradise's Season 3 finale airs next week and Viall is still on the show dating Jennifer Saviano, so the fact Viall is the franchise's new star came as a huge spoiler to fans.
"Well, can't talk spoilers, but Jen is an amazing woman -- one of the best. You'll have to watch to see how it ends. Obviously we don't end up together," Viall teased.
It's unclear whether Saviano breaks Viall's heart in Paradise or he chooses to end their romance, but according to previews for the finale, Viall is shown shaking his head in tears during the final Rose Ceremony, which doesn't look good for him.
Viall has had a lot of experience with The Bachelor franchise, but he still insisted to Collins and Lowe there is no real way to prepare for such an important role.
"I certainly have had the practice, right? But in all seriousness, I'm not sure anything prepares you for it. A lot of pushups," the 35-year-old software salesman joked.
"I think I'm definitely ready for it. I'm excited. I've had an interesting journey throughout this process and it hasn't worked out so far, and hopefully this time around, things will end up in a more positive way."
ABC's selection also came as a surprise because Viall was viewed as the villain on both of his The Bachelorette seasons. Men in the house didn't like him and thought he was arrogant, but Viall has certainly redeemed himself on Paradise.
FOLLOW REALITY TV WORLD ON THE ALL-NEW GOOGLE NEWS!
Reality TV World is now available on the all-new Google News app and website. Click here to visit our Google News page, and then click FOLLOW to add us as a news source!
"I made my mistakes, you know?" Viall confessed.
Viall then reiterated how the process of finding love on television again is "going to be great."
"It's going to be a lot of fun," he added. "I'm very nervous but I can't be more excited about the possibility of it actually working out."
As for what he looks for in a woman and his future wife? Well, it makes sense as to why he fell for Dorfman and Bristowe.
"I've always liked confidence... I've always been very attracted to women who are very confident and know their own self worth, someone who makes me a better person and challenges me and isn't afraid to give it as much as I like to," Viall explained.
The Bachelor's 21st season is set to premiere in January 2017.