Allie Lutz and Doug Reinhardt Credit: Instagram

Doug Reinhardt is engaged to Allie Lutz, the bride-to-be announced via Instagram Jan. 6!

Proudly sowing off her stunning 8-carat, pear-shaped diamond ring, Lutz's "high school sweetheart" gave his future wife a sweet peck in the picture. "Cat's out of the bag," the University of Southern California graduate, 26, wrote. "I proposed to her on a yacht in Anguilla that we rented for New Year's," Reinhardt tells Us Weekly. "We went island to island between St. Martin, St. Barts and and Anguilla."

Raised in Laguna Beach, Calif., Reinhardt, 28, briefly dated his Hills costar Lauren Conrad in the spring of 2008. He later dated actresses Amanda Bynes and Cassie Scerbo, hotel heiress Paris Hilton and former Miss USA Rima Fakih.

In addition to his career in reality TV, Reinhardt -- who attended attended Pepperdine University -- played baseball for the Los Angeles Angels of Anaheim and Baltimore Orioles. In 2010, he released a series of fitness DVDs, Reinhardt Kettebell System.

Reinhardt isn't the ony Hills star with a wedding in the works: Kristin Cavallari is planning to tie the knot with Chicago Bears quarterback Jay Cutler, father of her son, Camden, 4 months.