Breyer, who has served as an associate justice of the Supreme Court since 1994, made the announcement in a letter to U.S. President Joe Biden.
The 83-year-old liberal announced his retirement from the court earlier this year. He will be replaced by 51-year-old Ketanji Brown Jackson.
Jackson, who was nominated by Biden in late February and confirmed by the Senate in April, will be the first African American woman to serve on the U.S. Supreme Court.
Breyer's departure came less than a week after the Supreme Court's bombshell decision to overturn Roe v. Wade and eliminate constitutional protection to abortion rights.
Breyer and two other liberal justices dissented in a 66-page opinion.
Jackson, who has sat on the U.S. Court of Appeals for the D.C. Circuit since June 2021, is expected to be sworn in later this year. Before being elevated to the court of appeals, she served more than eight years as a judge on the U.S. District Court for the District of Columbia.
The Supreme Court is the final appellate court of the U.S. judicial system, with the power to review and overturn lower court decisions, and is also generally the final interpreter of federal law, including the nation's constitution.
The justices of the Supreme Court have life tenure and can serve until they die, resign, retire, or are impeached and removed from office.