Sandefjord is a city and the most populous municipality in Vestfold og Telemark county, Norway. The administrative center of the municipality. The municipality of Sandefjord was established on 1 January 1838. The municipality of Sandar was merged into Sandefjord on 1 January 1969. On 1 January 2017, rural municipalities of Andebu and Stokke were merged into Sandefjord as part of a nationwide municipal reform.

The city is known for its rich Viking history and the prosperous whaling industry, which made Sandefjord the richest city in Norway. Today, it has built up the third-largest merchant fleet in Norway. It is home to Europe's only museum dedicated to whaling, and is home to Gokstad Mound where the 9th century Gokstad Ship was discovered.

Sandefjord has numerous nicknames, including the Viking or Whaling "capital" of Norway. The city is also known as the "whaling capital of the world." It has also been dubbed the "Bathing City" (Badebyen), due to its many beaches and former resort spas. It is still considered a resort town, due to high numbers of visitors during summer months.

Sandefjord has become a transportation hub, home of Torp International Airport, one of Norway's largest airports. Daily ferry connections to Sweden are provided by Fjord Line and Color Line from the city harbor. European Route E18, one of Norway's most important roads, traverses the municipality.