"Today marks the 75th Anniversary of D-Day when troops landed on the beaches of Normandy to fight for our freedom," the young British royal captioned the pic.
"From my generation to yours: Thank You for your sacrifice, courage and strength. #dday75"
Fans commended Eugenie's powerful post on social media with floods of comments praising both Eugenie and the war veteran pictured in the photo.
"This photo just made me a mess," wrote one fan.
While one royal watcher commended not only Eugenie but also the Queen, "It was so wonderful to watch how your beloved Grandmother paid tribute to all the D-Day veterans, in her speech yesterday in Portsmouth. I love your Family."
American president Donald Trump and First Lady Melania Trump are currently in England for the official state visit and have met with the Duke of Cambridge and Kate Middleton, as well as accompanying other world leaders from across Europe for the D-Day celebrations.
Meghan Markle is the only family member to not attend any events over the last few days, as she is currently on maternity leave with little Archie Sussex.