Lance confirmed the news on Instagram with a photo of himself and Michael - who was sporting a gold engagement band. The caption read: "He said YES!! Love this man @michaelturchinart."
Michael also shared his excitement about the proposal, tweeting: "Happiest guy in the world :)"
Lance, 34, came out as gay in July 2006 in a cover story for an American magazine. He has since spoken about his desire to settle down. Two years ago he said: "I dream of having the family and the kids, and the parents want grandkids – that's all they care about, give me some grandbabies."
The engagement comes just one week after Lance reunited with Justin Timberlake and the other 'N Sync lads for a one off performance at the MTV Video Music Awards. It's certainly been a big week for the star.
Congratulations to the happy couple.