There are thirteen grounds for divorce in Georgia, the sixth of which is adultery. OCGA §19-5-3(6).
In Georgia, a person commits adultery when he/she voluntarily has sexual relations with a person other than his/her spouse. OCGA §16-6-19. The person with whom the spouse commits adultery does not have to be of the opposite sex. In fact, Georgialaw makes clear that extramarital homosexual relations are also considered adultery. Owens v. Owens, 247 Ga. 139, 140 (1981).
This ground can be difficult to prove, as a person often does not catch his/her spouse in the actual adulterous act. Most of the evidence is circumstantial so be sure to share everything youthink may be important with your attorney if you are seeking a divorce under this ground.
As an aside, the spouse who commits adultery is not eligible for alimony under Georgia law. Often times it becomes important to prove the adultery for this reason, rather than to prove thedivorce ground.