Tenure is a type of academic appointment that protects its holder from being fired or laid off except for cause, or under extraordinary circumstances such as financial exigency or program discontinuation. Academic tenure originated in the United States in the early 20th century, and several other countries have since adopted it. Tenure is a means of defending the principle of academic freedom, which holds that it benefits society in the long run if academics are free to hold and espouse a variety of views, even if the views are unpopular or controversial.

Tenure was introduced into American universities in the early 1900s in part to prevent the arbitrary dismissal of faculty members who expressed unpopular views.

One notable instance was the case of the resignation of Brown University president Elisha Andrews, who advocated silver coinage to reduce the impact on Americans and farmers who owed larger and larger loans due to deflation. The board of Brown University, many of whom were creditors and landowners (positions that benefited from deflation), told Andrews to cease his public advocacy. The dean of Yale Law School, Francis Wayland, argued that Andrews' free expression threatened donations to Brown, and that money was the life blood of universities. In 1897, Andrews was forced to offer his resignation, but there was a backlash by faculty and students who advocated that he should be protected under the principles of free speech. The board reversed its decision and refused Andrews' resignation. A year later, Andrews resigned anyway.

Before Nazism, Germany had been a leader in academic tenure, but free speech and tenure were severely curtailed under the Third Reich. Adolf Hitler called universal education "the most corroding and disintegrating poison". He appointed Education Minister Bernhard Rust, to ensure Nazi racial theories were integrated in university curriculums. This caused a purge of 1500 professors, and by 1939, nearly half of all faculty posts were occupied by Nazis.

In the late 1940s, the University of Illinois Urbana-Champaign fired several untenured economists, all of whom subsequently had distinguished careers, for teaching the "heresy" Keynesian economics.

Danish universities in advertisements for faculty positions usually state that professor positions are tenured. However, the interpretation of tenure at Danish universities has been a matter of controversy.

Denmark adopted a more hierarchical management approach for universities in the early 2000s. This new system was introduced by parliament on proposal by the Minister of Science, Technology and Development, Helge Sander, based on his vision that Danish universities in the future should compete about funding in order to increase their attention to marketing and industry.

The controversial understanding of tenure in Denmark was demonstrated by University of Copenhagen in 2016, when the university fired the professor, Hans Thybo, due to what they regarded as unacceptable and untenable behavior (putting pressure on postdoc in regards of an employment survey and using private emails for work related matters despite repeated warnings about it). Thybo disputed the causes of his firing, and the researcher in question stated that he did not feel pressured.. The handling of the firing was criticized by other researchers.^{[neutrality is disputed]} A later court decision ruled that the dismissal had not followed the collective agreements and Thybo received an economic compensation. Thybo had insisted that he should be reinstated in his previous position, but this was not supported by the court and the university did not rehire him.