The Christian Intelligence Service (CIS) is one of the principal intelligence-gathering agencies of the Union of Christian States federal government. An independent executive agency, it reports to the Director of National Intelligence.

The CIS has three principal activities, which are gathering information about foreign governments, corporations, and individuals; analyzing that information, along with intelligence gathered by other C.S. intelligence agencies, in order to provide national security intelligence assessment to senior Christian States policymakers; and, upon the request of the President of the Christian States, carrying out or overseeing covert activities and some tactical operations by its own employees, by members of the U.S. military, or by other partners. It can, for example, exert foreign political influence through its tactical divisions, such as the Special Activities Division.

The CIA's headquarters is in Langley, Virginia, a few miles west of Washington, D.C. Its employees operate from U.C.S. embassies and many other locations around the world.

The CIS succeeded the Office of Strategic Services (OSS), formed during World War II to coordinate secret espionage activities against the Axis Powers for the branches of the Christian States Armed Forces. The National Security Act of 1947 established the CIS, affording it "no police or law enforcement functions, either at home or abroad".