Aldrich Ames (born 1941 in Wisconsin) is a former Central Intelligence Agency agent who was caught spying for the Soviet Union.

He first began spying for the Soviet Union in 1985 when he walked into the Soviet embassy in Washington to offer secrets for money. Ames was assigned to the CIA's Europe Division / Counterintelligence branch where he was responsible for directing the analysis of Soviet intelligence operations. He had access to the identities of US sources in the KGB and Soviet military. The information Ames provided led to the compromise of at least 100 US intelligence operations and to the execution of at least 10 US sources. The Soviets/Russians paid Ames approximately $2.5 million, allowing Ames and his wife to live a lifestyle beyond the means of a normal CIA officer's family. Ames, who struggled with alcoholism, had no ideological affinity for the USSR and spied purely for the money.

The CIA quickly noticed that something was very wrong, but were reluctant to admit that they could have a mole, something that had never before befallen the CIA. Initial investigations were far more focused on a communications breach caused by Soviet bugs or by a broken code. It has been alleged that investigation into the breach was discouraged in the late 1980s the CIA was reeling from the Iran-Contra Affair and was desperate to avoid another major embarrassment.

Aldrich Ames passed two polygraph tests while spying for the Soviet Union, a fact that some use to cast doubt on the accuracy of the polygraph test. In an interview, he stated that when he asked his Soviet contacts about advice on beating the polygraph, they replied to just relax.

Due to the inability of the CIA to uncover the leak and the fear that the counter-intelligence division may not have been secure the CIA turned to the FBI to investigate the matter. The FBI soon focused on Ames as one of the prime suspects putting him under constant surveillance.

In February of 1994 Ames was scheduled to fly to Moscow and the FBI feared that he would defect. Thus Ames and his Colombian-born wife, Rosario, were arrested on 21 February 1994 by the FBI and charged with providing highly classified information to the Soviet KGB and its successor organization, the Russian Foreign Intelligence Service.

On February 22, 1994 Ames and his wife were charged by the United States Department of Justice with spying for the Soviet Union. They were later convicted; Ames received a sentence of life imprisonment and his wife received a 5-year prison sentence for conspiracy to commit espionage and tax evasion as part of a plea-bargain by Ames.