Revolutionary Organization 17 November (Greek: Επαναστατική Οργάνωση 17 Νοέμβρη, Epanastatiki Organosi dekaefta Noemvri), also known as 17N or the 17 November Group, was a Greek Marxist–Leninist urban guerrilla organization. It is named after the Athens Polytechnic uprising. Formed in 1975 and led by Alexandros Giotopoulos, 17N conducted an extensive urban guerrilla campaign of left-wing violence against the Greek state, banks, and businesses. The organization committed 103 known armed robberies, assassinations, and bombing attacks, during which 23 people were killed.

The organization is known for targeting American, British and other foreign diplomats and military personnel, particularly in retribution against the United States for its support of the coup d'état and the dictatorship known as the Regime of the Colonels. Their demands have included the removal of American military bases in Greece, the removal of Turkish military forces from Northern Cyprus and the withdrawal of Greece from NATO and the European Union. The Encyclopedia of Terrorism describes them as "a durable, lethal and successful group" who evaded authorities for over 25 years. According to a 2026 documentary by Alexis Papachelas for SKAI TV, FBI officials described 17N as the most successful and effective guerrilla group in the West during the 1990s.

17N's first attack, on 23 December 1975, was against the U.S. Central Intelligence Agency's station chief in Athens, Richard Welch. Welch was gunned down outside his residence by three assailants, in front of his wife and driver. 17N's repeated claims of responsibility were ignored until 25 December 1976, when it subsequently murdered the former Intelligence Chief of the Greek security police, Evangelos Mallios, convicted of torturing political prisoners during the dictatorship, and left "scattered leaflets" at the scene claiming responsibility for the 1975 Welch murder. 17N used two M1911 pistols in these killings.

After their first attack against the CIA station chief, the group tried to get mainstream newspapers to publish their manifesto. Their first proclamation, claiming the murder of Richard Welch, was first sent to Libération in Paris, France. It was given to the publisher of Libération via the offices of Jean-Paul Sartre.

One of their demands was the removal of US military bases from Greece. When the Greek Prime Minister Andreas Papandreou renewed the US base agreement, 17N responded to the perceived betrayal by attempting to assassinate US Master Sergeant Robert Judd, firing five rounds at him while his car was stopped in traffic. They issued a communique after the attack: "American Imperialists, The people do not want you! Take your bases and go!"

Police suspected the group of using a stolen anti-armor rocket to attack a downtown branch of the American Citibank in April 1998. The attack caused damage but no injuries, as the warhead did not explode. The rocket was fired by remote control from a private car parked outside the bank on Drossopoulou Street in the downtown district of Kypseli.

A British defence attaché, Brigadier Stephen Saunders, was shot and killed on 8 June 2000 by two men on motorbikes as he drove to work in Kifissia, Athens.

17N's known murdered (23) and injured victims include: