Extortion is a crime which involves the illegal acquisition of money, property, or favors through the use of force, or the threat of force. Historically, extortion was defined as an abuse of privilege on the part of a public official who used his or her position to get money or favors, but today, people at all levels of society could potentially commit extortion. Penalties for extortion vary, depending on the specifics of the crime. In some countries, extortion is treated especially seriously because it is linked with organized crime, and sometimes special laws are designed to make it easier to prosecute and punish extortion.

To the casual ear, extortion can sound very similar to blackmail, in which people use a threat to demand payments or favors, and robbery, in which a criminal takes something by force. However, extortion is slightly different from both of these crimes. In blackmail, someone threatens to do something which is entirely legal, such as publishing a set of photographs, with the blackmailee offering payment to avoid exposure and humiliation. Extortion is entirely illegal, as it involves threats of violence or other illegal acts.

In a robbery, the violence is very real, and also very immediate. In extortion, violence may never progress beyond the stage of being a threat, assuming that the person being extorted pays up. For example, if someone is threatened at gunpoint and ordered to surrender all valuables, this is a robbery. If, on the other hand, a criminal strolls into a shop and threatens to shoot the clerk's family unless the criminal receives a share of the store's income each week, this is extortion.

Organized crime is perhaps the most famous user of extortion. For example, members of the Mafia have historically demanded “protection money” from businesses, suggesting that if the businesses don't pay up, they may be robbed or otherwise harassed. Extortion has also been used to keep community groups in fear so that they will not seek prosecution for members of a criminal organization. However, individuals may also commit extortion, as may officials, especially in corrupt agencies or governments.

In order to prove charges of extortion, a prosecutor must be able to prove either that an illegal threat was made, or that goods or services were received in exchange for such a threat. Proving such charges can sometimes be very difficult, as people may be too intimidated to testify.