A leader circuit was an engineering component of the Constitution-class starships.

In 2266, aboard the USS Enterprise, after the main transporter circuits were damaged by a phaser blast, Chief Engineer Montgomery Scott attached some bypasses and leader circuits to compensate for the damaged circuits. This ad hoc arrangement would be tied into the impulse engines, with an acceptable five point variation in the velocity balance. In this way, the transporter was working normally. (TOS: "The Enemy Within")