Visby [ˈviːsbʏ] is a locality and the seat of Gotland Municipality in Gotland County, Sweden with 22,593 inhabitants, as of 2010. It is the only locality with historical city status on the island of Gotland; it is arguably the best-preserved medieval city in Scandinavia and has been named a UNESCO World Heritage Site. Among the most notable historical remains are the 3.4 km (2.1 mi) long town wall, that encircles the town centre.

The name "Visby" comes from the Old Norse Vis, (genitive singular of Vi) meaning sacrificial place, and by, meaning "city".

Visby is a popular vacation destination for Scandinavians during the summer and receives thousands of tourists every year. It is by far the most populated locality outside the Swedish mainland, with more than 22 000 inhabitants. Visby is also the only municipality seat of Sweden that is accessible only by boat and air traffic.