The Three Cities is the generic name given to the Maltese towns of Il-Birgu or Città Vittoriosa as well as Bormla or Città Cospicua and L-Isla-Senglea in Città Invicta, located on the island of Malta south of Grand Harbour. This name only appeared with the French occupation.

In the 17th century, the cities of Birgu and Senglea were the only fortified cities in this part of the island. In 1638, a new fortification, the Margherita Lines, encompassing Bormla, was built by the engineer Firenzuola. After the fall of Candia and the capture of Crete in 1670, the Grand Master of the Order of Saint John of Jerusalem Nicolas Cottoner y de Oleza asked Antonio Maurizio Valperga, military engineer of the Duke of Savoy, to build new fortifications encompassing all the hills above the Margherita Lines.

Cottoner, who was heavily criticised by the Catholic princes, provided funding for the work and laid the first stone on 28 August 1670. Behind his 4.5 kilometres of rampart encompassing towns and fields, Cottoner was thus able to shelter, if necessary, facing the fortifications of Valletta, 40,000 people with effects, food and livestock1.

Besides the expression "Three-cities", the name of this urban area in Latin is Civitas Cottonera, named after the great master who built the fortifications.