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 Wyoming, manslaughter is defined under Wyoming Statutes as the unlawful killing of a human being without malice. Wyoming law recognizes both voluntary and involuntary manslaughter. Voluntary manslaughter occurs when a person intentionally kills another in the heat of passion or under circumstances that would cause a reasonable person to become emotionally or mentally disturbed. Involuntary manslaughter in Wyoming involves the unintentional killing of another person through reckless or criminally negligent behavior, such as causing a fatal accident while driving under the influence of alcohol or drugs. Manslaughter is considered a felony in Wyoming and carries serious penalties, including imprisonment. The specific statutes detailing manslaughter and the associated penalties can be found in the Wyoming Statutes, typically within the criminal or penal code sections.