Third Echelon is a covert intelligence agency within the United States government, primarily featured in the Tom Clancy's Splinter Cell video game series. It operates under the National Security Agency (NSA) and focuses on counter-terrorism and intelligence gathering through advanced technology and espionage tactics. The agency is known for its use of elite operatives, such as Sam Fisher, who undertake high-stakes missions to neutralize threats. Third Echelon employs a range of tools, including surveillance equipment and stealth techniques, to achieve its objectives while maintaining secrecy and deniability in its operations.