During an appearance on Australian breakfast show 2DayFM Robbie said: "Ayda Field, I love you so much. Do you mind being my betrothed for the end of time?"
The brunette actress, who was in the studio at the time, laughed before replying: "I would love to be your betrothed 'till the end of time."
However, Robbie might not be permanently off the market just yet. The singer's manager later told GMTV that the proposal was just a bit of fun.
It took place after the show's presenter said that Sydney had a reputation for proposals.
Turning to Ayda, Robbie asked: "Is there anyone you want to get married to? Will you marry me?"
He then borrowed the host's frog ring and put it onto his girlfriend's engagement finger.
The 35-year-old singer was down under to attend the Australian Music Awards, where he performed his hit Bodies.
Nicole Kidman's other half Keith Urban was also there, though he lost out the battle for best country album to Maltese-Australian singer Troy Cassar-Daley.