"I am very excited to share with you guys that William and I got engaged over the weekend," Conrad, 27, wrote Sunday on her blog, where she also shared a snapshot of her new accessory: a diamond stunner. "I am beyond thrilled!"
Conrad's friends are just as excited for her strut down the aisle.
"Everyone is so happy for her. He's such a great guy. They are perfect for each other!" a source tells PEOPLE.
And fans should expect a behind-the-scenes look at the fashion designer's big day. "Get ready for lots more wedding content [on my blog] as we begin the planning process," she teased.
The California girl began dating Tell in 2012, when she told Allure, "You don't want a slob, but you don't want a guy who is constantly borrowing your tweezers.
Her sweet announcement comes on the heels of news her first serious boyfriend (and Laguna Beach love), Jason Wahler, married model Ashley Slack on Saturday.
Courtesy of Lauren Conrad