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 Kentucky, manslaughter is categorized into two degrees as per the Kentucky Revised Statutes. First-degree manslaughter, under KRS 507.030, is considered when a person intentionally causes another person's death under circumstances that would otherwise be murder, but the act is committed under the influence of extreme emotional disturbance. This is similar to the concept of voluntary manslaughter in other jurisdictions. Second-degree manslaughter, under KRS 507.040, occurs when a person's wanton or grossly negligent behavior results in another person's death. This aligns with the concept of involuntary manslaughter, such as when a person's reckless actions, like driving under the influence, lead to a fatal accident. Both degrees of manslaughter are felony offenses in Kentucky, with first-degree manslaughter classified as a Class B felony and second-degree manslaughter as a Class C felony. The penalties for manslaughter convictions in Kentucky can include substantial prison terms, with the possibility of enhanced penalties for aggravating factors.