Los Alcázares is a municipality and a coastal spa town and former fishing village on the western side of the Mar Menor in the autonomous community and province of Murcia, southeastern Spain.

The Mar Menor (little sea) belongs to three other municipalities: San Javier, San Pedro del Pinatar and Cartagena and is Europe's largest saltwater lagoon. Connected to the adjacent Mediterranean sea by several channels, the Mar Menor has a surface area of almost 20 sq km and the fact that it is typically 2-4 degrees warmer than the Mediterranean, makes it a very popular destination for sailing, windsurfing, kiteboarding and other water sports enthusiasts.

Los Alcazares has a resident population (2018) of 15,674 which rises to over 100,000 during the peak tourist summer holiday season.

On 13 October 1983, the town was granted municipal autonomy, in respect of which it holds an annual week-long celebration featuring live music, shows, windsurfing competitions and firework displays.

Besides the annual celebration of municipal autonomy, like many Spanish towns and cities, Los Alcazares also plays host to numerous fiestas and festivals throughout the year, including a large medieval market at the end of every March, and during the last two weeks in August, 'La Huerta' an international folklore festival and feast in celebration of the region’s status as the market garden of Spain.

Los Alcazares was used as a location for the 2008 movie of Ernest Hemingway's posthumous novel The Garden of Eden, starring Jack Huston, Richard E. Grant and Mena Suvari. A partly disused historic military air base at the southern end of the town was also used for location filming for the 2010 war movie, Green Zone featuring Matt Damon, Greg Kinnear and Jason Isaacs.