*In scuba diving, a diving regulator provides a diver with breathing gas at ambient pressure from a diving cylinder
*In automatic control, a regulator (automatic control) is a device which has the function of maintaining a designated characteristic. For example, a voltage regulator maintains a constant voltage.
*In a steam locomotive a regulator is the lever and associated valve which controls the passage of steam from the boiler to the cylinders.
*In social science, a regulator is an official responsible for control and supervision of an activity or area of public interest.
*In algebraic number theory, the regulator of a number field is a quantity defined from the group of units. After taking logarithms, it has the interpretation of the volume of a fundamental domain in the lattice (group) of units in logarithmic space .
*In Physics, a regulator is a construction used in regularization (physics) techniques.
*A battery regulator is a device in a battery pack which bleeds off excess charge current to let all cells reach full charge without overcharging some cells.
*In the United Kingdom Royal Navy, a Regulator is a naval policeman (or woman), a member of the Royal Navy Regulating Branch.
Regulators could be:-
*Members of the Regulator movement, a small-scale rebellion in North Carolina during the 1760s.
*Members of Shays Rebellion in 1786, also known as Shaysites.
*A Posse Comitatus (Common Law) formed during the Lincoln County War in the late 1870s. One of its members was Billy the Kid.