Ongi Monastery (Ongiin Khiid) is the collective name for the ruins of two monasteries that face each other across the Ongi River in Saikhan-Ovoo soum of Dundgovi province. The Bari Lam Monastery was built in 1810 on the north bank of the river while the Khutagt Lam Monastery was built in 1760 on the south. The older southern complex consisted of various administrative buildings as well as 11 temples and the northern complex consisted of 17 temples – among them one of the largest temples in all of Mongolia along with 4 Buddhist universities. It was one of the largest monasteries in Mongolia and housed over 1000 monks at its peak. The monastery was a place of devotion and scholarship until the complex was destroyed in the 1937 communist purges when over 200 lamas were murdered. Other people who were living nearby suffered and forced conscription into the communist army and, still others ran away to become herders. The ruins are situated about 18 km south of the Saikhan-Ovoo soum center.

Once, the communism fell in 1990s a small but growing contingent of monks arrived to set up temple amid the ruins, completing a small temple in 2004 and incorporating some original beams from the old ruined monastery in the new structure. A large number of ruins including a tall stupa can be seen on the bank of river and on its surrounding upsides. Currently, several monks live here full time, and every morning, before an altar flickering with candles and graced with a framed photo of the Dalai Lama, they worship and chant. Services begin at roughly 9am and last until about noon.