A criminal conspiracy is generally a partnership formed to commit a crime or crimes. A criminal conspiracy exists when two or more persons form an agreement to violate a law that includes criminal penalties, and then take one or more steps designed to accomplish the goal of the conspiracy.

Federal and state statutes make criminal conspiracies illegal for two primary purposes: (1) to help combat the powerful forces created when two or more people collaborate to commit a crime; and (2) to allow criminal prosecutors (state and federal) to prosecute persons who play a role in planning a crime but who are not involved in the physical acts taken to complete the underlying crime.

For example, under federal law, if two or more persons conspire either to commit any offense against the United States, or to defraud the United States, or any agency of the United States in any manner or for any purpose, and one or more of such persons do any act to accomplish the objective of the conspiracy, each of the conspirators may be fined under and imprisoned for up to five years. See 18 U.S.C. §371. And most states have statutes (usually located in the penal or criminal code) that make criminal conspiracies a crime and include significant punishment upon conviction.

In California, criminal conspiracy is defined under Penal Code Section 182 PC as an agreement between two or more persons to commit a crime and an overt act done by one or more parties to the agreement in furtherance of the conspiracy. The state recognizes the severity of collaborative efforts to commit crimes and aims to prosecute not only those who carry out the criminal acts but also those involved in the planning stages. The penalties for conspiracy in California vary depending on the underlying crime that was the object of the conspiracy, but they can be severe and include imprisonment and fines. This is in line with the federal law under 18 U.S.C. §371, which also criminalizes conspiracies to commit any offense against the United States or to defraud the United States, with penalties including fines and imprisonment for up to five years. Both state and federal laws reflect a concerted effort to deter and punish the collaborative nature of criminal conspiracies.