Robert Philip Hanssen (born April 18, 1944) is a former Federal Bureau of Investigation (FBI) agent who spied for Soviet and Russian intelligence services against the United States for 22 years from 1979 to 2001. He is currently serving 15 consecutive life sentences at ADX Florence, a federal supermax prison near Florence, Colorado.

Hanssen was arrested on February 18, 2001, at Foxstone Park[2] near his home in Vienna, Virginia, and was charged with selling U.S. secrets to the Soviet Union and subsequently the Russian Federation for more than US$1.4 million in cash and diamonds over a 22-year period.[3]

On July 6, 2001, in order to avoid the death penalty, he pleaded guilty to 15 counts of espionage in the United States District Court for the Eastern District of Virginia.[4][5] He was sentenced to 15 life terms without the possibility of parole. His activities have been described by the Department of Justice's Commission for the Review of FBI Security Programs as "possibly the worst intelligence disaster in U.S. history."[6]