Justin Timberlake -- I'm a Dad Now!!!

Justin Timberlake is a dad, which mean Jessica Biel is a mom.

Jessica just gave birth to Silas Randall Timberlake ... it appears the birth was early Saturday.

The baby and Jessica are doing well, so says the rep to People.

As for the name ... Justin's middle name is Randall, and his dad's first name is Randall.

As for Silas ... no clue.