United States Commission on International Religious Freedom Reauthorization Act of 2015

Amends the International Religious Freedom Act of 1998 to reauthorize the U.S. Commission on International Religious Freedom (USCIRF) as an independent federal government advisory body through FY2021.

Requires the USCIRF as a whole to have expertise on the variety of faiths practiced around the world.

Requires appointments to the USCIRF to be made within 90 days of a vacancy. Removes authority under which a USCIRF member may serve after the expiration of that member's term until a successor has taken office.

Amends the Foreign Service Act of 1980 to require the Secretary of State to receive assistance from the USCIRF when establishing training for Foreign Service officers in the field of internationally recognized human rights, including instruction regarding the relationship between religious freedom and security, as well as the role of religious freedom in U.S. foreign policy.

Encourages the Department of State to allow classified information to be accessed by USCIRF Commissioners and staff with the appropriate security clearance.

Requires discrimination on the basis of religion to be treated as a category of employment discrimination for purposes of the employment protections for USCIRF employees.

Revises restrictions on the USCIRF's acceptance of gifts and donations to permit sponsoring private parties to provide compensation and benefits to interns, fellows, and volunteers. Requires the number, duration, and funding source of any such internship, fellowship, or volunteer programs to be described in the USCIRF's annual financial report.