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 and second-degree manslaughter, as outlined in the Oklahoma Statutes, Title 21, Sections 711-716. First-degree manslaughter includes cases where a death occurs in the heat of passion but without a premeditated design, during a misdemeanor, or by a person engaged in another unlawful act that might produce death in an unlawful manner without due caution. Second-degree manslaughter occurs due to the lack of attention to a duty or law, essentially through gross negligence. Oklahoma does not explicitly label these as 'voluntary' or 'involuntary' manslaughter, but the concepts are similar. Manslaughter is considered a felony in Oklahoma, and the penalties can be severe, including imprisonment. The specific circumstances of the case, such as the defendant's intent, level of negligence, and presence of any aggravating factors, will influence the charges and potential sentencing upon conviction.