How many justice are currently on the US supreme court?

The US Supreme Court is currently comprised of 1 Chief Justice and 8 Associate Justices - for a total of 9 justices.

Article III of the United States Constitution gives Congress the authority to set the number of justices. The Judiciary Act of 1789 set the number at six justices. As the nation grew in size, more circuit courts were created and Congress added justices to correspond with the growing number of judicial circuits: seven in 1807, nine in 1837, and ten in 1863.

In 1866, Congress passed an act providing that the next three justices to retire would not be replaced, which would thin the bench to seven justices by attrition. One seat was removed in 1866 and a second in 1867. Before a third justice retired, the Circuit Judges Act of 1869 returned the number of justices to nine, and it has remained at 9 ever since.

In 1937 President Franklin D. Roosevelt was getting frustrated with the Supreme Court ruling that many of his programs were unconstitutional and attempted to convince Congress to expand the size of the court by appointing one additional justice for each incumbent justice who reached the age of 70 years 6 months and refused retirement, up to a maximum of 15 justices. He suggested that the additional justices would lighten the load on the most elderly justices, but his real motivation was quite transparent and the proposal went down in flames when voted upon by Congress.