John O'Brennan was an important leader in the United States government. He was the Director of the Central Intelligence Agency from 2013 to 2017. In that role, he was in charge of the CIA, which is the government agency responsible for gathering and sharing information about other countries and possible threats to the United States. He was also in charge of coordinating plans to protect America from danger, like terrorist attacks. John O'Brennan worked for the CIA for 25 years before becoming director, and he was responsible for making sure the CIA was able to do its job to keep the United States and its citizens safe.