In the United States, a special counsel (formerly called special prosecutor or independent counsel) is a lawyer appointed to investigate, and potentially prosecute, a particular case of suspected wrongdoing for which a conflict of interest exists for the usual prosecuting authority. Other jurisdictions have similar systems. For example, the investigation of an allegation against a sitting president or attorney general might be handled by a special prosecutor rather than by an ordinary prosecutor who would otherwise be in the position of investigating their own superior. Special prosecutors also have handled investigations into those connected to the government but not in a position of direct authority over the Justice Department's prosecutors, such as cabinet secretaries or election campaigns.

While the most prominent special prosecutors have been those appointed since the 1870s to investigate presidents and those connected to them, the term can also be used to refer to any prosecutor appointed to avoid a conflict of interest or appearance thereof. The concept originates in state law: "state courts have traditionally appointed special prosecutors when the regular government attorney was disqualified from a case, whether for incapacitation or interest." Because district attorneys' offices work closely with police, some activists argue that cases of police misconduct at the state and local level should be handled by special prosecutors.