Efraïn Jonckheer (20 October 1917 – 30 March 1987) was a businessman and politician of the Netherlands Antilles.

Jonckheer served as Prime Minister of the Netherlands Antilles from 8 November 1954 until 14 February 1968.

As of 2022, Jonckheer was the longest serving Prime Minister in the history of the Kingdom of the Netherlands.

In 1933, he obtained his mulo (junior high school) diploma, and became director of several businesses.

[4] In 1948 and 1952 until 1954, he was the representative of the Netherlands Antilles in the Round Table Conference about the future of the Dutch empire.