In the United States, a district attorney (DA), county attorney, state's attorney, prosecuting attorney, commonwealth's attorney, state attorney or solicitor is the chief prosecutor and/or chief law enforcement officer representing a U.S. state in a local government area, typically a county or a group of counties. The exact name and scope of the office varies by state. Alternative titles for the office include county attorney, solicitor, or county prosecutor. Generally the prosecutor represents the people of the jurisdiction and in many states their authority stems from the state constitution. Unlike similar roles in other common law judicial systems, these are appointed through partisan political processes, and their holders usually have an allegiance to a political party or faction, rather than being held by a career civil servant appointed on merit in an independent process.

The prosecution is the legal party responsible for presenting the case against an individual suspected of breaking the law, initiating and directing further criminal investigations, guiding and recommending the sentencing of offenders, and are the only attorneys allowed to participate in grand jury proceedings. The prosecutors decide what criminal charges to bring, and when and where a person will answer to those charges. In carrying out their duties, prosecutors have the authority to investigate persons, grant immunity to witnesses and accused criminals, and plea bargain with defendants.

A district attorney (or state attorney) leads a staff of prosecutors, who are most commonly known as assistant district attorneys (ADAs) or deputy district attorneys (DDAs) in states which have state attorneys the staff attorneys are usually referred to as Assistant State Attorneys (ASAs). Most prosecutions will be delegated to ADAs, with the district attorney prosecuting the most important cases and having overall responsibility for their agency and its work. Depending upon the state's law, DAs may be appointed by the chief executive of the jurisdiction or elected by local voters. Most criminal matters in the United States are handled in state judicial systems, but a comparable office for the United States Federal government is the United States Attorney.