Yes, adultery is illegal in Wisconsin on paper. It is classified as a Class I felony, punishable by up to $10,000 in fines and up to three years and six months in prison.1Wisconsin State Legislature. Wisconsin Statutes 939.50 – Classification of Felonies In practice, no one gets charged. The statute is a nineteenth-century relic that prosecutors do not enforce, and Wisconsin’s divorce system is no-fault, so proving an affair rarely changes what happens in court. The one place infidelity can actually cost a spouse money is when marital funds were spent on the relationship.
What the Criminal Statute Says
Wisconsin Statute 944.16 covers two situations: a married person who has sex with someone other than their spouse, and any person who has sex with someone they know is married to another person.2Wisconsin State Legislature. Wisconsin Statutes 944.16 – Adultery That second clause means the affair partner is technically exposed too, even if they are single themselves.
Prosecutions are essentially nonexistent. By 1990, Wisconsin lawyers could not recall the last time a county prosecutor tried to enforce the statute. The evidence is private, juries are reluctant to convict, and district attorneys have no interest in cases that consume resources without a public safety benefit. Treating this law as a genuine criminal risk would be misleading, but it does remain on the books.
Does Adultery Affect a Wisconsin Divorce?
Not in the way most people expect. Wisconsin is a purely no-fault state. The only recognized ground for divorce is that the marriage is “irretrievably broken.”3Wisconsin State Legislature. Wisconsin Statutes 767.315 – Grounds for Divorce and Legal Separation If both spouses agree, the court accepts it. If only one spouse says the marriage is over, the court may order a waiting period of 30 to 60 days before making a final determination.
Proving your spouse cheated does not speed the case up, change the grounds, or give the filing spouse any procedural edge. The court does not ask why the marriage failed. That is a deliberate policy choice: Wisconsin keeps fault out of the divorce process itself.
Where an Affair Can Actually Shift the Money: Marital Waste
Wisconsin starts from a presumption that marital property is divided equally, and the statute expressly says courts may adjust that split “without regard to marital misconduct.”4Wisconsin State Legislature. Wisconsin Statutes 767.61 – Property Division So the affair on its own does not tilt the division.
The real exposure is marital waste. If a spouse spent significant marital money on the affair (hotel rooms, gifts, trips, rent for an apartment shared with an affair partner), the other spouse can argue those expenditures wasted marital assets. The property statute lets courts weigh “other economic circumstances of each party” and any other factor the court finds relevant when adjusting the division.4Wisconsin State Legislature. Wisconsin Statutes 767.61 – Property Division
A successful marital waste claim is not a punishment. It corrects the math. If one spouse spent $30,000 on the affair, the court can credit the other spouse an equivalent amount from the remaining assets or shift related debts.
The burden of proof falls on the spouse alleging the waste. You need documentation. Credit card statements, bank records, receipts. Vague accusations that money was spent irresponsibly will not carry a claim. Timing matters too. Waste from years before the divorce filing is harder to prove than spending in the months leading up to the split, and it may carry less weight.
Maintenance
Adultery is not on the list of factors that determine spousal maintenance. Courts look at length of the marriage, each spouse’s age and health, earning capacity, education, time out of the workforce, and the marital standard of living.5Wisconsin State Legislature. Wisconsin Statutes 767.56 – Maintenance The statute has a catch-all for any other factor the court finds relevant, but courts have not used that provision to turn maintenance into a penalty for infidelity.
An affair can matter indirectly if it produced a real financial consequence. If the unfaithful spouse drained savings or ran up debt, the court can account for that reality when setting maintenance. The focus stays on financial impact, not the moral dimension.
Child Custody
Custody decisions turn on the best interests of the child. The statute lists more than a dozen factors, including each parent’s wishes, the child’s adjustment to home and school, cooperation between the parents, substance abuse, and any history of abuse.6Wisconsin State Legislature. Wisconsin Statutes 767.41 – Custody and Physical Placement Adultery is not one of them.
Context can still reach the analysis. If a parent’s affair exposed the child to instability, brought someone with a concerning background into the household, or caused the parent to be absent or neglectful, those facts can affect the court’s view of the child’s adjustment, the quality of parenting time, or the mental health of adults in the proposed household. The affair is never the issue on its own. The question is whether the child’s wellbeing was affected.
Prenups With Infidelity Clauses
Wisconsin recognizes marital property agreements under Statute 766.58. To be enforceable, an agreement must have been signed voluntarily, with fair and reasonable financial disclosure from both sides, and it cannot be unconscionable at the time it was made.7Wisconsin State Legislature. Wisconsin Statutes 766.58 – Marital Property Agreement
Some prenups include infidelity clauses that impose specific financial consequences: reducing the unfaithful spouse’s share, or increasing the other spouse’s maintenance. Wisconsin courts can enforce these, within limits. A clause that imposes wildly disproportionate penalties, functioning as punishment rather than a reasonable financial adjustment, could be found unconscionable. Courts evaluate whether the overall result is fair.
Triggering the clause takes actual evidence. Text messages, financial records, or testimony from someone with direct knowledge. The spouse seeking to enforce it carries the burden. If your prenup does not contain an infidelity clause, adultery has no effect on how the agreement is applied.
You Cannot Sue the Affair Partner
Some states still let a spouse sue the person their partner had an affair with under theories called alienation of affection or criminal conversation. Wisconsin abolished both entirely. Statute 768.01 goes further than eliminating existing claims: it says no act done within Wisconsin can give rise to these causes of action, whether the suit would be filed in Wisconsin or in another state.8Wisconsin State Legislature. Wisconsin Statutes 768.01 – Actions for Alienation of Affection Abolished
There is no path to recover money from a third party who was involved in your spouse’s affair. Any remedy has to come from the divorce case itself.
Military Service Members Face a Different Rule
If either spouse is an active-duty service member, the calculus changes. Under the Uniform Code of Military Justice, Article 134, adultery can be charged as a criminal offense when the conduct is prejudicial to good order and discipline or brings discredit on the armed forces. Maximum punishment includes a dishonorable discharge, forfeiture of all pay and allowances, and confinement for one year.
The military weighs the service member’s rank, whether government time or resources were used, the impact on unit morale, whether the service member continued the relationship after being ordered to stop, and how public the situation became. A single service member can face charges if the person they were involved with is married. Unlike Wisconsin’s civilian statute, the military enforces its version, and a conviction can end a career, strip retirement benefits, and leave a criminal record that follows someone into civilian life.