Claye became the fifth Olympian to propose during the games after 27-year-old Harrison, herself a hurdler and former Olympian, with a huge diamond ring.
Claye said: 'When I woke up this morning I was like, "Today is going to be the best day of my life.'"
'I'm going to go out there and do what I have to do on the track first and I am going to make her my fiancée after that.'
He climbed over a railing before being helped up a wall and into the seating area where he found Harrison before dropping to one knee on the row of seats in front.
Harrison played it cool for a moment, resting her chin in her hand as she gave a quizzical look, before saying yes as the pair shared an emotional hug.
'I told her she was my best friend. I told her she was my rib. I told her I want to grow old with her,' Claye recounted.
'I want her to be by my side for the rest of my life. She's helped me to grow into the man I am today.'