The United States Court of Appeals for the First Circuit (in case citations, 1st Cir.) is a federal court with appellate jurisdiction over the district courts in the following districts:

• District of Maine
• District of Massachusetts
• District of New Hampshire
• District of Puerto Rico
• District of Rhode Island

The court is based at the John Joseph Moakley Federal Courthouse in Boston, Massachusetts. Most sittings are held in Boston, where the court usually sits for one week most months of the year; in one of July or August, it takes a summer break and does not sit. The First Circuit also sits for one week each March and November at the Jose V. Toledo Federal Building and United States Courthouse in Old San Juan, Puerto Rico, and occasionally sits at other locations within the circuit.^[1]

With six active judges and four active senior judges, the First Circuit has the fewest judges of any of the thirteen United States courts of appeals. Since retiring from the United States Supreme Court, Associate Justice David Souter has occasionally sat on the First Circuit by designation.

As of June 23, 2023^[update]:

Chief judges have administrative responsibilities with respect to their circuits, and preside over any panel on which they serve, unless the circuit justice (the Supreme Court justice responsible for the circuit) is also on the panel. Unlike the Supreme Court, where one justice is specifically nominated to be chief, the office of chief judge rotates among the circuit judges.

To be chief, a judge must have been in active service on the court for at least one year, be under the age of 65, and have not previously served as chief judge. A vacancy is filled by the judge highest in seniority among the group of qualified judges, with seniority determined first by commission date, then by age. The chief judge serves for a term of seven years, or until age 70, whichever occurs first. If no judge qualifies to be chief, the youngest judge over the age of 65 who has served on the court for at least one year shall act as chief until another judge qualifies. If no judge has served on the court for more than a year, the most senior judge shall act as chief. Judges can forfeit or resign their chief judgeship or acting chief judgeship while retaining their active status as a circuit judge.^[3]

When the office was created in 1948, the chief judge was the longest-serving judge who had not elected to retire, on what has since 1958 been known as senior status, or declined to serve as chief judge. After August 6, 1959, judges could not become or remain chief after turning 70 years old. The current rules have been in operation since October 1, 1982.^[4]

The court has six seats for active judges, numbered in the order in which they were initially filled. Judges who assume senior status enter a kind of retirement in which they remain on the bench but vacate their seats, thus allowing the U.S. President to appoint new judges to fill their seats.

• West v. Randall (1820), one of the first decisions setting precedent for class action suits

• Courts of the United States
• Judicial appointment history for United States federal courts#First Circuit
• List of current United States circuit judges
• List of United States federal courthouses in the First Circuit