Paternity law is a branch of family law that legally establishes parenthood. The paternity suit is usually brought by an unwed mother against the father of a child. In married couples, the husband is automatically assumed to be the biological father of any children produced in the marriage. If the husband wishes, he can contest the paternity of a child and absolve himself from legal duties to care for the child.

Paternity is established using a DNA test between the mother, father, and child in question. This is usually done with a saliva swab, but may also be done by a blood test. Once the biological father is determined, he can then be held liable for custody and child support.

Certain family law attorneys specialize in paternity suits or can assist in paternity matters during regular divorce or child support proceedings.