The Amaravati Mahachaitya (Stupa) is a ruined Buddhist monument, probably built in phases between the third century BCE and about 250 CE, located within city limits of Amaravathi village of Guntur district.

The monument was not called a stupa in ancient inscriptions, but rather the mahachaitya or great sanctuary. The earliest inscription from the site belongs to the early centuries BCE but it cannot be assigned to Ashoka with certainty. In the early period, the stupa had a simple railing consisting of granite pillars, with plain cross-bars, and coping stones. The coping stones with youths and animal reliefs, the early drum slabs, and some other early fragments belong to this period. The stupa must have been fairly large at this time, considering the size of the granite pillars.

The discovery of Mahachaitya as one of the most ancient Buddhist edifices was through the help of the Asokan pillar edict and the Northern Black Polished ware. The site possesses a one-of-a-kind brick-built circular vedika with five octogonal ayaka pillars. The indications of Mahayana Buddhism giving way to Tantricism in Dhanyakata was evident with the presence of bronze coins and select stone images of Maitreyi, Manjusuri, Lokeswara, Vajrapani and Heruka of the Vajrayana sect.

The ruins of the Stupa at Amaravati were first found after a visit in 1797 by Major Colin Mackenzie. On the right bank of the Krishna River, Mackenzie came across a huge Buddhist construction built of bricks and faced with slabs of limestone. By the time he returned in 1816, indiscriminate excavations had already destroyed what remained of the structure and many of the bricks had been reused to build local houses. Mackenzie carried out further excavations, recorded what he saw and drew a plan of the stupa.

Maha Chaitya was enlarged several times by Ikshvaku kings, who succeeded Satavahanas, reaching its final form between 3rd & 4th centuries AD. Clad in local white limestone, it was an earthen hemispherical mound about 148 ft in diameter and more than 98 feet high, including its supporting drum and capping finial. It was surrounded by 6 mtr high railing with posts and cross pieces.

The stupa was was carved with panels that tell the story of Buddha. The story of the sculpture, including their discovery, misuse and destruction and subsequent preservation & distribution to various museums (Chennai, Calcutta, London, Masulipatnam etc. ) has been poignantly described by Shimada. During the period of the decline of Buddhism, this stupa was neglected and was buried under rubble. A 14th-century inscription in Sri Lanka mentions repairs made to the stupa, and after that it was forgotten. The stupa is related to the Vajrayana teachings of Kalachakra, still practiced today in Tibetan Buddhism.

All of the sculptures have been removed from the site of the Mahachaitya, although a few broken pillars remain. Museums across India and around the world have specimens from Amaravati. These collections are being brought together in the World Corpus of Amaravati Sculpture, a digital project agreed to and jointly developed by the Archaeological Survey of India and the British Academy, London. The Amaravati Collection, sometimes called the Amaravati Marbles, is a series of 120 sculptures and inscriptions in the British Museum from the Amaravathi Mahachaitya. It consists of over 120 different pieces made from a limestone called Palnad marble; although the material is certainly not marble and the source of the stone in the Palnad quarry not decisively proven.

The site is now under the protection of the Archaeological Survey of India. The campus includes the stupa itself and the Archaeological Museum. The important sculptures from the site are now in a number of museums in India and abroad. Mahachaitya of Amaravathi can be visited during timings 8:00 AM - 6:00 PM. Today, the stupa is the only example of an Ashokan pillar to have been found in the whole of South India. Many buddhist devotees visit the stupa to offer their prayers. Visitors shall be required to show photo identity proof in original at the entry to the monument. Edibles are not allowed inside the monument. A nominal entrance fee of INR 15 is charged for Indians and INR 200 for foreigners.