Manslaughter is the unlawful killing or homicide of a human being without the premeditation or malice (malice aforethought) required for the criminal offense of murder.

Many states have two types of manslaughter: (1) voluntary manslaughter—the defendant intended to kill the victim, but did so in self-defense, or in the heat of passion and without premeditation, or the defendant was insane and did not understand that the killing was wrong; and (2) involuntary manslaughter—the defendant negligently or recklessly caused the death of another person—such as when a person is intoxicated while operating a motor vehicle and causes an accident that results in the death of another person.

Some states do not have separate criminal offenses for voluntary and involuntary manslaughter—these states may have the offense of manslaughter and identify certain aggravating factors that may enhance the penalties upon a conviction for manslaughter.

Manslaughter is a felony offense and may be punished by a lengthy prison term. Manslaughter laws are generally located in a state's statutes—often in the penal or criminal code.

In Wisconsin, manslaughter is not specifically defined as a separate offense in the state statutes; instead, Wisconsin law categorizes unlawful killings under different degrees of homicide. The state recognizes 'First-Degree Reckless Homicide' under Wis. Stat. § 940.02, which is similar to involuntary manslaughter and involves reckless conduct leading to death. 'Second-Degree Reckless Homicide,' under Wis. Stat. § 940.06, involves deaths caused by reckless actions without the intent to kill, akin to a lesser degree of involuntary manslaughter. Wisconsin also has a provision for 'Homicide by Intoxicated Use of Vehicle or Firearm' under Wis. Stat. § 940.09, which addresses killings resulting from operating a vehicle or firearm while under the influence. While Wisconsin does not have a statute specifically named 'voluntary manslaughter,' situations that might be considered voluntary manslaughter in other states could fall under 'First-Degree Intentional Homicide' (Wis. Stat. § 940.01) with mitigating circumstances that could reduce the charge to 'Second-Degree Intentional Homicide' (Wis. Stat. § 940.05). Manslaughter-equivalent offenses in Wisconsin are felony offenses and can result in significant prison terms, with the exact penalties varying based on the degree of the offense and the circumstances surrounding the killing.