"This was taken in 1996, when I just started working in movies. It was one of my very first photo shoots ... I was beyond excited to have the chance to work in film," Witherspoon captioned the pic. "20 years later, I still am ❤."
"I love being an actor, traveling the world, and learning about other people's lives," she continued. "Feeling very grateful for my amazing job! #TBT #90sFashion."
ET caught up with Witherspoon ahead of Sunday's Academy Awards, where she gushed about Emma Stone's future Best Actress win, explaining that winning the award was a "lifelong dream" for her before her own 2006 win.
"I'm always getting emotional when people win," she shared. "It's a lifelong dream and it's a very small group of people. And you feel very honored to be a part of it."
"It's very fun and exciting," she added. "I get excited for people."