The actress posted the snap, from 1996, showing the two fresh-faced stars looking remarkably similar to their 2020 selves.
Oscar-winner Witherspoon, 44, would have been around 20 when the picture was taken and stared into the camera while wearing bright red lipstick.
The famously youthful Rudd, 51, would have been around 27 at the time of the photograph and smiled while leaning his head against Witherspoon’s.
The pair first starred together in 1998 rom-com Overnight Delivery and later in 2010’s How Do You Know.
Witherspoon wrote in the caption: “Wait a second… did #PaulRudd and I take the ‘Selfie’ in 1996?”
Her celebrity friends shared their thoughts in the comments section.
Wonder Woman actress Gal Gadot wrote: “Trendsetter.”
Wedding Crashers star Isla Fisher said: “The original.”
And writer, director and actress Lena Waithe declared Witherspoon “always ahead of your time.”
The throwback picture delighted fans, with many focusing on Rudd’s youthful looks.
“This is confirmation that Paul Rudd indeed has a time machine,” one said.
And another asked: “Paul Rudd seriously doesn’t age! How does he look the same as he did in 1996??”
