Franeker (Dutch pronunciation: [ˈfraːnəkər] ^ⓘ; West Frisian: Frjentsjer [ˈfrjɛntsjər]) is one of the eleven historical cities of Friesland and capital of the municipality of Waadhoeke. It is located north of the Van Harinxmakanaal and about 20 km (12 mi) west of Leeuwarden. As of 2023, it had 13,015 inhabitants. World Heritage Site the Eise Eisinga Planetarium, established in 1781, is located in the city.

Franeker was founded around 800 as a Carolingian stronghold. The name probably derives from Froon-acker, meaning 'land of the lord/king'; the oldest street in the city is still called Froonacker. Beginning around the 11th century, Franeker developed into the administrative center of northern Westergoa.

Franeker received city rights in 1417, when it was recognised as an independent city and, through the Buurbrief ('Citizen's letter'), formally separated from the grietenij Franekeradeel [nl].

At the end of the 15th century, Albert, Duke of Saxony established himself in Franeker, when he had taken over Friesland with the help of the Schieringers led by Hessel van Martena [nl]. On 12 May 1500, the city was besieged by an army of 16,000 dissatisfied Frisians during the Siege of Franeker [nl], as a result of the high rents and taxes levied by Albert and his sons Henry and George of Saxony. Henry established his seat in the city of Franeker. The Frisians achieved nothing with the siege of the city because they were poorly trained and organised. Duke Albert of Saxony hastily assembled a large army to relieve Henry and the city of Franeker. Finally, the Frisians were defeated on 16 July 1500 and the city was relieved. On 26 March 1501, Henry IV of Saxony gave the city of Franeker a considerable (200 morgen) piece of salt marshland outside the dike, called the Franekerlanden. Three years later, Henry handed over the government of Friesland to his brother George.

Franeker seemed to become the capital of Friesland at the end of the 15th century. In 1504, however, the Saxons fled to Leeuwarden. After that, the city remained important to the Saxons for a long time, until Friesland was transferred as a possession to Charles V in 1524.

When the Dutch Republic revolted against the Spanish Empire, Franeker chose the side of William of Orange early on. In 1579, Friesland joined the Union of Utrecht in the joint fight against Spain. In 1580, the States of Friesland decided that only the Reformed doctrine was permitted. In order to meet a growing demand for ministers, lawyers, and doctors, the States decided to found a university.

As such, a Protestant university, the University of Franeker, the oldest in the Netherlands after the University of Leiden, was established on 29 July 1585. The university was housed in the former monastery building of the Crosiers. At this Academy of Friesland, donated by the Frisian stadtholder William Louis, one could study theology, law, medicine, classical languages, philosophy, mathematics, and physics. Some notable students include William IV, Prince of Orange, Peter Stuyvesant, René Descartes, and Eise Eisinga. It was closed shortly after the incorporation of the Kingdom of Holland into the French Empire, when Napoleon Bonaparte closed the academy in 1811. A successor institution, the Rijksatheneum, was founded in 1815, but in 1847 it, too, closed.

In 1984, the municipalities of Franeker and Franekeradeel [nl], as well as part of the municipality of Barradeel, were merged into the new municipality of Franekeradeel.