Ajusco is a 3,930 m (12,894 ft) lava domevolcano located just south of Mexico City, Mexico, in the Tlalpan borough of the city. It is the highest point in the Mexican Federal District, which contains Mexico City.

Ajusco is a Náhuatl word variously translated as "source of waters" or "watered grove", and the Lerma River and Balsas River draw some of their source waters from this area. Also, the flow from all of the remaining strong springs in the area adjacent to the peak are captured to augment Mexico City's water supply.

Ajusco is a lava-dome complex of Pliocene-Pleistocene age, surrounded by block-and-ash flow deposits. Ajusco is part of the mountain chain of volcanic origin known as Sierra del Ajusco-Chichinauhtzin, among which Xitle (3,128 m/10,262 ft), Tláloc (3,690 m/12,106 ft), Pelado (3,620 m/11,877 ft), Cuautzin (3,510 m/11,516 ft) and Chichinautzin (3,470 m/11,385 ft) stand out. This range is part of the Trans-Mexican Volcanic Belt which crosses central Mexico and contains the country's highest peaks.