The judiciary (also known as the judicial system or judicature) is a coequal branch of government. It is the only branch that is supposed to be totally impartial and hence apolitical. The judiciary forms a system of courts which interprets the law in the name of the sovereign or state. The judiciary also provides a mechanism for the resolution of disputes. Under the doctrine of the separation of powers, the judiciary can never make or enforce law, that being the realm of the legislative and executive branches respectively, but rather, if there is a dispute, it interprets and applies the law to the facts of each case. Unlike the legislative branch which can make, repeal and amend law at will according to its own rules, the judiciary can never make or amend law, rather only when a statute or executive order is found via judicial review to be in violation of a constitutional provision is the judiciary bound to strike it or part of it down. If a statute is found to be unconstitutional, it is left for the legislative branch to come up with another legislation dealing with the issue which is always presumed constitutional by the judiciary.

This branch of government is often tasked with ensuring equal justice under law. It usually consists of a court of final appeal (called the "supreme court" or "constitutional court"), together with lower courts.

The term "judiciary" is also used to refer collectively to the personnel, such as judges, magistrates and other adjudicators, who form the core of a judiciary (sometimes referred to as a "bench"), as well as the staffs who keep the system running smoothly.