Udayagiri is the largest Buddhist complex in the Indian state of Odisha. It is composed of major stupas and monasteries (viharas). Together with the nearby complexes of Lalitgiri and Ratnagiri, it is part of the "Diamond Triangle" of the "Ratnagiri-Udayagiri-Lalitgiri" complex. It used to be thought that one or all of these were the Pushpagiri Vihara known from ancient records, but this has now been convincingly located at a different site. Per epigraphical artifacts found at the site, Udayagiri's historical name was "Madhavapura Mahavihara." This Buddhist complex, preceded by the Ratnagiri and Lalitgiri sites, with their monasteries, is believed to have been active between the 7th and the 12th centuries.

Lalitagiri is a major Buddhist complex in the Indian state of Odisha. The complex is home to stupas, 'esoteric' Buddha images, and monasteries (viharas), which is the oldest site in the region. Significant finds at this complex include Buddha's relics. Tantric Buddhism was practiced at this site.