Austin Crecelius proposed to Allison Boyle (Allie) just before the drop on The Voyage Rollercoaster at the popular park.
When the ride started, he told Allie "you once told me life was like a rollercoaster... and it's a lot more fun to go with another person".
As the carriage climbed higher, he continued: "I wanted to ask you if you'd be my rollarcoaster buddy".
"Allie, will you marry me?"
Allie began weeping as the rollarcoaster began it's speedy descent, and the crying couple screamed as it plummeted.
Austin's friends recorded the whole thing over their shoulder from the seats in front and Austin uploaded the video to his YouTube page, where it amassed over half a million views.
Austin and Allie took to the page to apologise to the Park after some commenters pointed out that the camera was not allowed on the ride. Austin wrote that it was "brought to my attention that bringing a video recording device onto a roller coaster violates safety protocol".
"I want to apologize to Holiday World for breaking that rule and for any trouble this video may have caused".