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 York, manslaughter is categorized into two degrees as defined in the New York Penal Law. First-degree manslaughter (Section 125.20) is similar to voluntary manslaughter and occurs when a person intends to cause serious physical injury and ends up causing the death of another person, or when a death is caused under circumstances that demonstrate a depraved indifference to human life. Second-degree manslaughter (Section 125.15) is akin to involuntary manslaughter and involves a person recklessly causing the death of another person. Manslaughter in New York is considered a felony offense. The penalties for manslaughter convictions are severe and can include lengthy prison sentences. First-degree manslaughter can result in up to 25 years in prison, while second-degree manslaughter can lead to a maximum of 15 years in prison. These laws are detailed in the penal code and reflect New York's approach to differentiating between levels of culpability in unlawful killings without the premeditation required for murder.