St. John's (Antiguan and Barbudan Creole: Sen Jaan) is the largest city of Antigua and Barbuda. It is located in the western part of Antigua, surrounding St. John's Harbour. The city is Antigua and Barbuda's primate city, having a population of 22,219. St. John's also tends to dominate the parish of Saint John, which composes much of the city's metropolitan area. From its establishment after the French invasion in 1666, the city has rapidly grown, eventually replacing Falmouth as the island's dominant city.

After its establishment, St. John's became an official trading point in 1675. By 1689, St. John's had overtaken Falmouth in population. St. John's continued to grow throughout the 1700s, occasionally being impacted by a fire or hurricane. St. John's has largely been spared from armed conflict, although a large-scale slave revolt was planned in the city in 1736.

St. John's is not necessarily a tourist destination, as it primarily functions as the country's economic centre. St. John's is home to Antigua State College, the country's largest higher education institution, and an open campus of the University of the West Indies. St. John's is attempting to modernise its economy, being home to many convention centres and contemporary office buildings. St. John's is also home to the national library and most government agencies. St. John's is the origin of the All Saints Road corridor, in which most of the country's population lives. While St. John's completely dominates its metropolitan area, the city's economy has stimulated that of surrounding areas like Piggotts and Cedar Valley. While St. John's houses all three branches of government, no law has declared St. John's the official capital city. Most diplomatic missions are located in the nearby village of Marble Hill.