In the snap, the royal could be seen with her nose pressed against her other half's cheek, with Jack grinning from ear to ear as he looked at the camera.
WATCH: Princess Eugenie sends special message on ICAP Charity Day
"This time 3 years ago… flashback to such a happy moment when Jack and I announced our engagement..." the mum-to-be captioned her photo.
Eugenie shared the photo on Instagram
It wasn't long until heaps of sweet comments began to pile up beneath Eugenie's photo.
"Such a beautiful couple," wrote one.
"Such a cute couple, loved watching your wedding!" added another, with a third writing: "You look so happy."
Eugenie and Jack are expecting their first child together in mid-February and they have been preparing for the arrival of their little one at Windsor's Frogmore Cottage.
The couple are expecting their first child next month
The couple, who married in October 2018, were living in three-bedroom Ivy Cottage, in the grounds of Kensington Palace, but with Frogmore Cottage empty since Prince Harry and Meghan moved to the US, Eugenie has been handed the keys.
Needless to say, the internet is currently abuzz with possible baby name choices, and we've been given a big hint at the possibilities from betting site Betfair, who have revealed that two names are frontrunners for the royal baby.
Betfair spokesperson Sam Rosbottom said: "Royal fans are excited to kick off 2021 with another baby due next month - and expect Eugenie and Jack to stick with traditional names, with Alice and Arthur, both at 8/1 currently leading the way in the betting."
"They are followed by the likes of Godfrey, Grace and Henry at 10/1, while it is interesting to see Charles at 22/1 and Edward at 25/1 should they decide to name it after the baby's grandfather or great-uncle."
Make sure you never miss a ROYAL story! Sign up to our newsletter to get all of our celebrity, royal and lifestyle news delivered directly to your inbox.