The 25-year-old announced her new status Tuesday on Instagram, posting a photo of the duo with a romantic sunset in the background.
"I love you more than I have words to express. Josh, you’re my best friend and my soulmate," she wrote. "I can’t wait for forever together. Yes a million times over ?."
Joshua followed up the post with his own announcement, uploading a picture of Karlie and misspelling his new label for her. "fiancé ❤," he wrote.
The couple, who've been together for six years, has been in the spotlight most recently for Joshua's connection to President Trump. The entrepreneur is the younger brother of Jared, Ivanka Trump's husband and a senior advisor to the president.
While they have yet to announce details surrounding their wedding, we can bet Karlie's former BFF, Taylor Swift, will not be apart of their special day.