|Prime Minister of Greece|
21 April 1967 – 13 December 1967
|Preceded by||Panagiotis Kanellopoulos|
|Succeeded by||Georgios Papadopoulos|
|Died||13 July 1998|
Kollias was Attorney General during the period 1941-1944 when Greece was occupied by three Axis forces (Germany, Italy and Bulgaria). He was responsible for persecuting resistance members during the occupation, and was indicted after liberation for his actions. According to a published study by Dimitris Kousouris (2014: p.155) 
...he was not only never suspended while his case was pending, but he was also assigned to organize the work of the Special Collaborators’ Courts (SCC). He was finally acquitted solemnly by his colleagues some months later, with praise “for carrying out his duties under the irregular conditions of foreign occupation.” [...] [S]ymbolizing the continuity of the [right-wing authoritarian] judicial and state apparatus in postwar Greece, Konstantinos Kollias became better known for his later feats as attorney general who tried to stop the inquiry on the murder of a left-wing deputy Grigoris Lambrakis in 1963 and as Prime minister of the colonels’ junta in 1967.
Kollias was proclaimed Prime Minister by the far-right Greek military junta of 1967–74 on 21 April 1967, the very day of the coup d'état that overthrew Panagiotis Kanellopoulos' legitimate government. However, nearly eight months later, he was replaced by the head of the military coup d'état Georgios Papadopoulos after the unsuccessful counter-coup of King Constantine II on 13 December 1967.
Kollias died on 13 July 1998, at the age of 96. From 15 January 1998, when former India Prime Minister Gulzarilal Nanda died, until his own death, Kollias was the world's oldest living former head of government.
| Prime Minister of Greece
| Oldest living state leader
15 January 1998 – 13 July 1998
Ion Gheorghe Maurer