Looks like young love is eternal!

Sarah Michelle Gellar took to Instagram to wish her Buffy the Vampire Slayer costar David Boreanaz a very happy birthday!

RELATED: If You Thought Smith Jerrod was Hot on Sex and the City, JUST WAIT Until You See Him Today!

The mom-of-two, 39, posted a collage of the newly 47-year-old.

“When you hear it’s someone’s birthday, and you realize how long you’ve known them,” she captioned the sweet tribute. “Happy birthday David. Immortality looks good on you.”

Even though Buffy has been off the air for years, the two remain close friends.

“David and I will always have a connection and we will always remain friends,” she gushed back in 2014.

For access to all our exclusive celebrity videos and interviews – Subscribe on YouTube!