Turner announced the news via Instagram over the weekend, and Williams reacted with this adorable post:
"Congratulations to my beautiful girlfriend on her engagement," she wrote on Monday, alongside a snap of Turner's engagement ring.
"This is just one of MANY life milestones we'll share," Williams added.
The heartfelt message delighted thousands of her fans. Her addition of the #jophie hashtag, however, captivated them even more.
By reworking the #mophie hashtag that she and Turner regularly use, she appeared to signal her approval.