The 59-year-old actor has been dating the former shop assistant for almost a year, and although she has refused to marry him four times already, he has gone down on one knee yet again.
It is unclear if Roberts accepted the latest proposal.
Hasselhoff posted a picture of the couple in Sydney, Australia, with the words “Tried it again on top of the Sydney harbour bridge! (sic)” and followed it up with another shot of the pair kissing.
Recalling the previous proposals, Hayley has said: “The first time was on a beautiful beach in South Africa. David got down on one knee and asked me. I just laughed. I didn’t think he meant it, because there was no ring and I thought it was a spur-of-the-moment thing. Actually, if I’d said yes I thought he might have had a heart attack.
“The second time, he was getting ready in the dressing room at the awards show. Again, I didn’t say no – I just laughed.
“[The third time] we were swimming in a cage surrounded by sharks, which was scary. When we came out of the water he asked me again. I was too cold to answer.
“Another time, we were on safari and he got out of the car, stood in front of an elephant and asked if I’d marry him. That time I didn’t laugh. I was screaming because I could see the elephant was about to charge towards him.”