Notifying the Court
If you suspect your spouse has forged your signature, contact your divorce court. As a party to the litigation, you can get copies of all the paperwork associated with your case. You can review the documents' signatures. If any of them are not yours, tell the court clerk. Procedures for contesting the entry of a decree vary from state to state. The court clerk will be able to tell you what to do next and may schedule you to meet with the judge who granted the divorce. You may have to file a motion to vacate the judgment. If so, you may need proof that the signature isn’t yours, such as testimony from a handwriting expert.
Involvement of Law Enforcement
Forgery is a form of fraud, so law enforcement will most likely get involved. Your spouse not only committed the offense against you; he deceived the court as well -- and by extension, the state. Even if you decide not to press charges, the state probably will. Criminal charges against your spouse might include forgery, perjury, unsworn falsification and criminal impersonation. He might go to jail for committing fraud against the state, because this is "extrinsic" fraud and is more serious than fraud committed against a private individual. The fraud your spouse committed against you would probably be a civil matter, punishable by restitution if his deceit cost you money, or punitive monetary damages to you for the stress he’s caused.
If you confront your spouse with your suspicions, he might attempt to make excuses. However, there are virtually no circumstances under which he can legally sign your name to divorce papers. Even if you once gave him power of attorney to sign documents for you and you never revoked it, he can’t use it to sign legal divorce documents. He is the other party in the litigation; he’s personally involved. If your spouse denies forging your signature and you're not absolutely sure he did, you might want to consult with an attorney before you take another step, because the repercussions can be serious.
If you don’t bring the forgery to the attention of the court because you don’t want your spouse to go to jail, you’re stuck with the divorce decree or settlement agreement your spouse signed. You have no choice but to adhere to it, even if it gives him custody of your children and all your property. The only way you can get out of it is to inform the court of what occurred. The court will probably nullify your divorce decree if the signature on it is not yours.