The 30-year-old former American Idol star tweeted, "I'M ENGAGED!!!!! I wanted y'all to know!! Happiest night of my life last night! I am so lucky and am with the greatest man ever :)"
Blackstock is a talent manager and is also the son of Clarkson's manager, Narvel Blackstock, who is married to Reba McEntire. The newly engaged couple have been together for a year.
They Dated?! Surprising Celebrity Hookups
Star Sightings: Celebrity Candids
Are These Celebs Too Tan?! Cast Your Vote!