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 Oklahoma, manslaughter is categorized under two main types: first-degree manslaughter and second-degree manslaughter. First-degree manslaughter includes cases where the killing is perpetrated without premeditation but in the heat of passion or while committing a misdemeanor. It also covers situations where a death occurs unintentionally but in an imminently dangerous manner showing a depraved mind. Second-degree manslaughter occurs when the death is a result of the defendant's lack of due caution or circumspection, which can be seen as an act of negligence or recklessness. Oklahoma does not explicitly label these as 'voluntary' or 'involuntary' manslaughter, but the concepts are similar. Manslaughter is a felony in Oklahoma, and the penalties can be severe, including lengthy prison terms. The specific statutes governing manslaughter can be found in the Oklahoma Statutes, Title 21, which outlines the state's penal code.