Sant Antoni de Portmany is a town and municipality located on the western coast of Ibiza within the Balearic Islands autonomous community of Spain. Situated on Sant Antoni Bay, it serves as the second-largest town and municipality on the island. The settlement occupies a strategic position along the west-facing coastline, defining its geographical character and administrative role within the region.

For two thousand years, the area functioned as a small fishing village rising from the Roman natural harbor known as Portus Magnus. Significant growth began in the late 1950s when hotels and tourist resorts were constructed as part of a mass tourism initiative across Spain. Development spread around San Antonio Bay to Cala de Bou, while the 1980s saw British tourists become the majority of summertime visitors.

The town features distinct districts such as the West End, centered on Carrer de Santa Agnès, and the Sunset Strip along the coast. Notable landmarks include the Egg statue, erected in the early 1990s to commemorate claims regarding Christopher Columbus's birthplace, and Passeig de ses Fonts, a harbourside promenade developed in the early 1990s with illuminated fountains and palm trees.

Sant Antoni is renowned for its vibrant nightlife, hosting bars featuring house, rock, and indie music, as well as DJs like Swedish House Mafia. Visitors gather at venues such as Café del Mar to watch sunsets. The area also celebrates the fiesta of Saint Bartholomew on 24 August with massive fireworks displays, attracting young British clubbers who view it as a premier destination for nightlife.

The municipality has a population of 24,937 as of 2025. Its economy relies heavily on tourism, supported by ferries to Formentera and connections to Barcelona and Palma de Mallorca during the season from May until September or October. Access is facilitated by Ibiza Airport, with taxi and bus services available, including direct buses during peak summer seasons.