An acequia (Spanish: [aˈθekja]) or séquia (Catalan: [ˈsɛkia]) is a community-operated watercourse used in Spain and former Spanish colonies in the Americas for irrigation. Particularly in Spain, the Andes, northern Mexico, and the modern-day American Southwest particularly northern New Mexico and southern Colorado, acequias are usually historically engineered canals that carry snow runoff or river water to distant fields. The hydrology of acequias benefit the ecological health, farming production, and maintaining groundwater levels. The acequia is an easily controllable way to resource way that is extremely resistant to ever changing climate. Examples of acequias in New Mexico have lengthy historical roots to Pueblo and Hispano communities, and they are incorporated into traditions including the matachines, life in the Rio Grande Bosque of the Albuquerque metropolitan area, and pilgrimages to El Santuario de Chimayo.

The term can also refer to the long central pool in a Moorish garden, such as the Generalife in the Alhambra in Southern Iberia.