The Australian world number nine and Britain's top women's player have been dating for several years with their news sparking congratulations from across the tennis world.
"We've been keeping a small secret," the pair jointly said on Instagram late Monday, with Boulter showing off her ring.
Among the well-wishers were women's stars Paula Badosa and Madison Keys while de Minaur's fellow Australian Thanasi Kokkinakis quipped: "It's about damn time."
De Minaur, 25 and Boulter, 28, both enjoyed breakthrough seasons in 2024.
The Australian broke into the top 10 for the first time while Boulter reached a career-high 23.
They both start their 2025 campaigns at the mixed-teams United Cup in Sydney this week.
