Timberlake, who turns 31 later this month, is believed to have popped the question to Biel, 29, while the two were holidaying at a luxury ski resort in Wyoming.
A source confirmed to Us Weekly magazine that, 'Justin knows how much she loves snowboarding and the mountains, so it was the perfect place.
'He knew it was the right time to propose.'
The couple have been dating on-and-off for over four years.
