Celebrity dads who are celebrating Father's Day for the first time

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