What body is responsible for setting the number of Supreme Court justices?

The body responsible for setting the number of Supreme Court justices is Congress. This authority stems from Article III of the United States Constitution, which allows Congress to determine the structure of the federal judiciary, including the Supreme Court. While the Constitution does establish the Supreme Court, it does not specify the number of justices, leaving that decision to Congress.

Over time, Congress has changed the number of justices on the Supreme Court several times, and it holds the power to do so as it sees fit. This power is part of the checks and balances system within the government, allowing the legislative branch to have a significant role in shaping the judicial branch.