Do I legally have to give my baby the father's last name if we are not married? NJ resident.

No, but he may be able to force having his name on the because

No, you do not have to

As said, no you don't have to. Actually as soon as the baby is born he/she gets your last name automatically. It isn't until the next day that you do the formal name papers (I know from experience). This is when you pick what your child will be called if you want you can keep your last name or place his last name on the birth cirtificat though if he is going to sign the paper swearing he is the father (because you aren't married) he may want to have a say. Also as said he can fight and possibly get it changed afterward by going to court and petitioning for a name change and judges can order a name change including on the birth cirtificate. But simple answer is no. Just be aware it MAY change if the father wants.