Hauz Khas Complex, Medieval building complex in South Delhi, India

Hauz Khas Complex is a medieval site in South Delhi district that includes a water reservoir, an Islamic seminary, a mosque, a tomb, and several pavilions. The buildings stand in an L-shape around the large tank that once supplied water to the surrounding area.

Alauddin Khalji built the water tank in the early 14th century to supply the nearby Siri Fort. Firoz Shah Tughlaq added the teaching buildings and his own mausoleum between 1352 and 1354.

The name Hauz Khas comes from the Persian hauz (water tank) and khas (royal), so it means "Royal tank"; the tank was first called Hauz-i-Alai after Alauddin Khalji. The madrasa, founded in 1352, taught astronomy, mathematics, medicine, calligraphy, grammar and rhetoric, later adding Sanskrit, and was funded by donations from the royal court. The village around it was known as Tarababad, "city of joy".

The site has several entrances and connected paths that make it easy to explore the grounds. Visitors can reach adjacent areas like Deer Park and nearby metro stations on foot.

The tank was originally about 50 hectares, measuring roughly 600 m by 700 m with 4 m of water depth, and was first called Hauz-i-Alai after Alauddin Khalji. Its storage capacity at the end of each monsoon was reported as 0.8 M. Timur, who camped at Hauz Khas in 1398, noted that each side of the stone- and stucco-lined tank was longer than an arrow's flight.