A misdemeanor (American English,^[1] spelled misdemeanour in British English) is any "lesser" criminal act in some common law legal systems. Misdemeanors are generally punished less severely than felonies, but theoretically more so than administrative infractions (also known as minor, petty, or summary offences) and regulatory offences. Many misdemeanors are punished with monetary fines.

A misdemeanor is considered a crime of low seriousness, and a felony one of high seriousness.^[2] A principle of the rationale for the degree of punishment meted out is that the punishment should fit the crime.^[3][4][5] One standard for measurement is the degree to which a crime affects others or society. Measurements of the degree of seriousness of a crime have been developed.^[6]

In the United States, the federal government generally considers a crime punishable with incarceration for one year or less to be a misdemeanor. All other crimes are considered felonies.^[7] Many states also employ the same or a similar distinction.^[8]

The distinction between felonies and misdemeanors has been abolished by several common law jurisdictions (notably the UK^[9] and Australia).^[10] These jurisdictions have generally adopted some other classification (in the UK the substance of the original distinction remains, only slightly altered): in the Commonwealth nations of Australia,^[11] Canada,^[12] New Zealand,^[13] and the United Kingdom,^[14][15] the crimes are divided into summary offences and indictable offences.^[16] The Republic of Ireland, a former member of the Commonwealth, also uses these divisions.^[17]

In the United States, even if a criminal charge for the defendant's conduct is normally a misdemeanor, sometimes a repeat offender will be charged with a felony offense. For example, the first time a person commits certain crimes, such as spousal assault, it is normally a misdemeanor, but the second time it may become a felony.^[18] Other misdemeanors may be upgraded to felonies based on context. For example, in some jurisdictions the crime of indecent exposure might normally be classified as a misdemeanor, but be charged as a felony when committed in front of a minor.^[19]

In some jurisdictions, those who are convicted of a misdemeanor are known as misdemeanants (as contrasted with those convicted of a felony who are known as felons). Depending on the jurisdiction, examples of misdemeanors may include: petty theft, prostitution, public intoxication, simple assault, disorderly conduct, trespass, vandalism, reckless driving, discharging a firearm within city limits, possession of cannabis and in some jurisdictions first-time possession of certain other drugs, and other similar crimes.

Misdemeanors usually do not result in the loss of civil rights, but may result in loss of privileges, such as professional licenses, public offices, or public employment. Such effects are known as the collateral consequences of criminal charges. This is more common when the misdemeanor is related to the privilege in question (such as the loss of a taxi driver's license after a conviction for reckless driving), or when the misdemeanor involves moral turpitude—and in general is evaluated on a case-by-case basis.

In the United States, misdemeanors are typically crimes with a maximum punishment of 12 months of incarceration, typically in a local jail as contrasted with felons, who are typically incarcerated in a prison. Jurisdictions such as Massachusetts are a notable exception where the maximum punishment of some misdemeanors is up to 2.5 years.^[20] People who are convicted of misdemeanors are often punished with probation, community service, short jail term, or part-time incarceration such as a sentence that may be served on the weekends.

The United States Constitution provides that the President may be impeached and subsequently removed from office if found guilty by Congress for "high crimes and misdemeanors". As used in the Constitution, the term misdemeanor refers broadly to criminal acts as opposed to employing the felony-misdemeanor distinction used in modern criminal codes.^[21] The definition of what constitutes a "high crime" or "misdemeanor" for purposes of impeachment is left to the judgment of Congress.^[22]

In Singapore, misdemeanors generally are sentenced to months of jail sentence but with individual crimes suspects are sentenced to a harsher sentence. The penalty of vandalism is a fine not exceeding S$2,000 or imprisonment not exceeding three years, and also corporal punishment of not less than three strokes and not more than eight strokes of the cane.

Depending on the jurisdiction, several classes of misdemeanors may exist; the forms of punishment can vary widely between those classes. For example, the federal and some state governments in the United States divide misdemeanors into several classes, with certain classes punishable by jail time and others carrying only a fine.^[23] In New York law, a Class A Misdemeanor carries a maximum sentence of one year of imprisonment, while a Class B Misdemeanor "shall not exceed three months".^[24]

In the United States, when a statute does not specify the class of a misdemeanor, it may be referred to as an unclassified misdemeanor.^[25] Legislators usually enact such laws when they wish to impose penalties that fall outside the framework specified by each class. For example, Virginia has four classes of misdemeanors, with Class 1 and Class 2 misdemeanors being punishable by twelve-month and six-month jail sentences, respectively, and Class 3 and Class 4 misdemeanors being non-jail offenses payable by fines.^[26] First-time cannabis possession is an unclassified misdemeanor in Virginia punishable by up to 30 days in jail rather than the normal fines and jail sentences of the four classes.^[26][27] New York has three classes of misdemeanor: A, B, and Unclassified.^[28]

All distinctions between felony and misdemeanour were abolished by section 1(1) of the Criminal Law Act 1967. Prior to this, a person prosecuted for misdemeanour was called a defendant.^[29]