The United States Junior Chamber, also known as the Jaycees, JCs or JCI USA, is a leadership training and civic organization for people between the ages of 18 and 40. It is a branch of Junior Chamber International (JCI). Areas of emphasis are business development, management skills, individual training, community service, and international connections. The U.S. Junior Chamber is a not-for-profit corporation/organization as described under Internal Revenue Code 501(c)(4).

Established as the United States Junior Chamber of Commerce on January 21, 1920, it provided opportunities for young men to develop personal and leadership skills through service to others. The Jaycees later expanded to include women after the United States Supreme Court ruled in the 1984 case Roberts v. United States Jaycees that Minnesota could prohibit sex discrimination in private organizations. 1985 marked the final year of the U.S. Jaycee Women (also known as Jayceettes or Jayceens), an organization that lasted 10 years and at its convention in 1984 in Atlanta boasted 59,000 members.

At its membership peak in 1976, the U.S. Jaycees boasted a membership total of 356,000 men between the ages of 18 and 35. Rules were later changed to allow members to stay active until age 40.