The 28-year-old pilot got down on one knee on night two of The Bachelorfinale, which aired on Tuesday, proposing to Hannah Ann Sluss during his emotional final rose ceremony.
"I remember that very first night, giving out that first impression rose -- there was never a question to be as to who it was going to," he said. "I know I told you that I was falling for you, and I told you that my heart was being torn in two different directions. And now, I have to follow my heart."
"Madison, she left two days ago," he revealed, growing teary-eyed. "My heart chooses you forever. I love you, Hannah Ann, and the love that you've shown me is all that I have ever wanted."
As Hannah Ann expressed her shock at being his final choice, Peter got down on one knee to officially pop the question. She immediately said yes, exclaiming, "I can't believe you're all mine!"
Peter's proposal came after the shocking self-exit of his other finalist, Madison, who left Australia before the Bachelor was able to hand out his final rose.
Madison and Peter's relationship hit a roadblock right before fantasy suites, as she warned him she wouldn't be able to move forward in their relationship if he had slept with the other women. On what was supposed to be their overnight date, Peter confessed he had been intimate with someone else.
Still, Peter told ET at the Women Tell All taping last month that he didn't consider Madison's warning to be an ultimatum.
"I don't feel like it was an ultimatum. I don't," he said. "I think it was her doing what I asked every girl to do from the very first night and that was to be honest with me and share what was ever on their heart. And that's what she did."
"Trust me, it made it an insanely incredibly difficult week for me. There's no doubt about that," Peter added. "But I can't fault her for sharing her heart."
The Bachelor continues Tuesday at 8 p.m. ET/PT on ABC. ET's Lauren Zima will be recapping everything that goes down, directly after the episodes. Watch ET Live on your Roku, Apple TV or Amazon Fire TV or you can stream on Pluto TV and Samsung TV Plus.