Their names are known by billions across the world, but to their newborns at home, these celebrities are better known as "dad."
Some celebrity dads are gearing up to celebrate their first Father's Day.
Justin Timberlake
Ryan Reynolds
Bryan Singer
But other veteran celebrity dads are still doing their best to figure out this whole fatherhood thing.
Jim Gaffigan
Conan O'Brien
James Van Der Beek
Jimmy Kimmel
Max Greenfield