Konstantinos G. Karamanlis (Greek: Κωνσταντίνος Γ. Καραμανλής, pronounced [konstaˈdinos karamanˈlis]; 8 March 1907 – 23 April 1998) was a Greek statesman who was the four-time Prime Minister of Greece and two-term president of the Third Hellenic Republic, serving in the former role from 1955 to 1963 and from 1974 to 1980. A towering figure of Greek politics, his political career spanned portions of seven decades, covering much of the latter half of the 20th century.

Born near Serres in Macedonia, Karamanlis practiced law until his election to the Hellenic Parliament in 1936 as a member of the conservative People's Party. Rising through the ranks of Greek politics after World War II, Karamanlis became Minister of Labour in 1947, and in 1951 he was named Minister for Public Works in Alexandros Papagos's Greek Rally administration. He was appointed prime minister by King Paul of Greece after Papagos's death in 1955. During his first term, he applied a program of rapid industrialization, heavy investment on infrastructure and improvement on agricultural production, which led to the post-war Greek economic miracle. He also implemented the extension of full voting rights to women, which had stood dormant since 1952. In foreign affairs, he pursued an aggressive policy toward Greek membership in the European Economic Community (EEC), and abandoned the government's previous strategic goal for enosis (the unification of Greece and Cyprus) in favour of Cypriot independence.

In 1963, Karamanlis resigned following a disagreement with King Paul amidst spiralling political crises in Greece. He spent the next eleven years in self-imposed exile in Paris, while the country fell under military dictatorship after the 1967 coup d'état. After the fall of the junta in 1974, Karamanlis was recalled to Athens to assume interim premiership. This period, known as the Metapolitefsi, saw the country's transition to a pluralist democracy. His new party, New Democracy, won a commanding victory in the November 1974 elections, which were followed by a plebiscite that abolished the monarchy and established the Third Hellenic Republic.

In 1980, Karamanlis resigned as prime minister and was elected President of the Republic. In 1981, he oversaw Greece's formal entry into the European Economic Community. He resigned from the presidency in 1985 but was again elected in 1990, and served until his retirement from active politics in 1995. Karamanlis died in 1998 at the age of 91.

Karamanlis was born in the village of Proti, near the city of Serres, Macedonia, which was then part of the Ottoman Empire. He became a Greek citizen in 1913, after the region of Macedonia was annexed by Greece in the aftermath of the First and Second Balkan War. His father was Georgios Karamanlis, a teacher who fought during the Greek Struggle for Macedonia, in 1904–1908. After spending his childhood in Macedonia, he went to Athens to attain his degree in law. He practised law in Serres, entered politics with the conservative People's Party, and was elected Member of Parliament for the first time in the 1936 election at the age of 28. Health problems^{[citation needed]} prevented him from participating in the Greco-Italian War.

During the Axis occupation, he spent his time between Athens and Serres, while in July 1944, he left to the Middle East to join the Greek government in exile.

After World War II, Karamanlis quickly rose through the ranks of Greek politics. His rise was strongly supported by fellow party-member and close friend Lambros Eftaxias, who served as Minister for Agriculture under the premiership of Konstantinos Tsaldaris. Karamanlis's first cabinet position was Minister for Labour in 1947 under the same administration. In 1951, along with most prominent members of the People's Party, Karamanlis joined the Greek Rally of Alexandros Papagos. When this party won the Greek legislative election on 9 September 1951, Karamanlis became Minister of Public Works in the Papagos administration. He won the admiration of the US Embassy for the efficiency with which he built road infrastructure and administered American aid programs. When Papagos died after a brief illness (October 1955), King Paul of Greece appointed the 48-year-old Karamanlis as prime minister. The King's appointment took the Greek political world by surprise, as it bypassed Stephanos Stephanopoulos and Panagiotis Kanellopoulos, two senior Greek Rally politicians who were widely considered as the heavyweights most likely to succeed Papagos. After becoming prime minister, Karamanlis reorganized the Greek Rally as the National Radical Union. One of the first bills he promoted as prime minister implemented the extension of full voting rights to women, which stood dormant although nominally approved in 1952. Karamanlis won three successive elections (February 1956, May 1958 and October 1961).

In 1959 he announced a five-year plan (1959-64) for the Greek economy, emphasizing improvement of agricultural and industrial production, heavy investment on infrastructure and the promotion of tourism, setting the bases of the post-WWII Greek economic miracle, though implementation was disrupted by the 1967 Coup d'état and the 7 years of dictatorship that followed.