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 New Jersey, manslaughter is categorized under N.J.S.A. 2C:11-4 as either aggravated manslaughter or manslaughter, which can be considered analogous to voluntary and involuntary manslaughter, respectively. Aggravated manslaughter occurs when someone causes a death under circumstances manifesting extreme indifference to human life, and it is a crime of the first degree. Manslaughter in New Jersey, which can be seen as voluntary manslaughter, involves recklessly causing death or committing a homicide in the heat of passion resulting from reasonable provocation, and it is a crime of the second degree. Involuntary manslaughter, typically characterized by reckless or negligent behavior that leads to someone's death, is also covered under the manslaughter statute. Manslaughter in New Jersey is a serious felony offense, and those convicted may face substantial prison terms, with the degree of the offense and the associated penalties determined by the specific circumstances of the case.