Sierre (French pronunciation: [sjɛʁ] ; German: Siders [ˈzidərs]; Arpitan: Siérro [ˈʃiʁo] ) is the capital municipality of the district of Sierre, located in the Rhône valley in the canton of Valais, Switzerland. It has a population of 18,020. Sierre is nicknamed City of the Sun (French: Cité du Soleil) for its average of 300 days of sunshine a year.

It is the last official French-speaking city in Valais before the French–German language border of the canton located at the forêt de Finges, a few kilometres after the town. A German-speaking minority lives in Sierre, counting for around 8% of the population.

Sierre was first mentioned around 800 as Sidrium, though a 12th-century document refers to the village being founded in 515.