The Naval Criminal Investigative Service (NCIS) is the United States Department of the Navy's primary law enforcement agency and successor to the former Naval Investigative Service (NIS).

Roughly half of the Naval Criminal Investigative Service (NCIS) 2400 employees are civilian special agents. They are trained to carry out a wide variety of assignments at locations across the globe. NCIS special agents are armed federal law enforcement investigators and frequently coordinate with other US government agencies. NCIS special agents are supported by analysts and other experts skilled in disciplines such as forensics, surveillance and surveillance countermeasures, computer investigations, physical security, and polygraph examinations.