Titan Rain was a string of cyber operations that compromised a number of agencies within the U.S. and UK government. Chinese state-sponsored actors are suspected of breaching the unclassified networks of the U.S. Departments of State, Homeland Security, and Energy, and UK defense and foreign ministries. Although the attacks were first publicly revealed in 2005, the United States reported that they had been ongoing since at least 2003. The United Kingdom reported that the campaign continued as late as 2007.

Titan Rain was the first instance of state-sponsored espionage from China that was made public, triggering a decades-long effort by the U.S. government to reduce the breadth and scope of Chinese cyber operations against U.S. targets.