The caption reads: "16 year old Meghan Markle [poses] with her first boyfriend Luis Segura at a high school Christmas dance in 1997".
The post gathered over 63,000 likes, with many Instagram users stunned at how little the Duchess seems to have changed.
"She still looks the same, good genes," commented one, with another saying, "She hasn't changed."
Another added: "You could have told me that was taken last year and I'd wholeheartedly believe you."
Meghan's high school teacher Ilise Faye said she was "always a leader among her school friends' and "stood up for the underdog".
Faye, who taught the Duchess until she was 13 years old, said that school was always important to Meghan.
"Learning was important and she had a voice."
