Ioannis Metaxas (Ιωάννης Μεταξάς, 12 April 1871 – 29 January 1941) was a Greek military officer and politician who was dictator of Greece from 1936 until his death in 1941. He governed constitutionally for the first four months of his tenure, and thereafter as the strongman leader of the 4th of August Regime following his appointment by King George II.

Born to an aristocratic family in Ithaca, Metaxas took part in the Greco-Turkish War of 1897 and the Balkan Wars (1912–13), and quickly rose through the ranks of the Hellenic Army. As a monarchist during the National Schism, Metaxas unsuccessfully opposed Prime Minister Eleftherios Venizelos and Greece's entry in World War I; he was exiled to Corsica in response in 1917. On his return, Metaxas moved into politics and founded the Freethinkers' Party, but had only limited success under the Second Hellenic Republic.

Metaxas was appointed prime minister in April 1936, a year after the Greek monarchy was restored. With the support of King George II, Metaxas initiated a self-coup and established an authoritarian, nationalist, and anti-communist regime, which Metaxas himself and some historians called totalitarian. The ideology and system associated with his rule, Metaxism, has been described as a form of Fascism, or a conventional authoritarian-conservative dictatorship, or a regime with a strong fascist component.

On 28 October 1940, Metaxas rejected an ultimatum imposed by the Italians to surrender, committing Greece to the Allies and bringing the country into the war. He died in January 1941, before the German invasion and subsequent fall of Greece.