Chief Justice is the title of the presiding judge of a supreme court. The term can apply to state or federal chief justices, but is mostly used in reference to the Chief Justice of the U.S. Supreme Court.
Chief justices are the most senior member of the court, regardless of how many years they served on the bench. As the most senior member of the court, they generally write the majority opinions when in the majority, which allows them to influence the historical record. In addition to holding the duties of the associate justices, chief justices have duties unique to their position. For example, federally, this includes the duty to preside over presidential impeachment trials under Article I, Section 3 of the Constitution.
In the federal judiciary, Article III does not explicitly create an office of the Chief Justice, but the Constitution presupposes its existence by referring to it in the impeachment clause of Article I. The Judiciary Act of 1789 formally creates the office of the Chief Justice. The process for selecting a Chief Justice of the U.S. Supreme Court is the same as for associate Justices, i.e. nomination by the President and affirmation by the Senate. The current Chief Justice of the U.S. Supreme Court is Chief Justice John Roberts.
At the state level, states may provide for the office of the Chief Justice in their constitution or in other legislation. For example, Article 6, Section 2 of the California Constitution explicitly provides that “[t]he Supreme Court consists of the Chief Justice of California and 6 associate justices.”
[Last updated in December of 2021 by the Wex Definitions Team]