Ujjain (also known as Ujain, Ujjayini, Avanti, Avantikapuri), is an ancient city of Malwa in in central India on the eastern bank of the Kshipra River (today part of the state of Madhya Pradesh. It is the administrative centre of Ujjain District and Ujjain Division.

In ancient times the city was called Ujjayini. As per epic Mahabharata Ujjayani was the capital of Avanti Kingdom. It has been the first meridian of longitude for Hindu geographers since the 4th century BCE. It is one of the seven sacred cities of the Hindus, and the Kumbh Mela religious festival is held there every twelve years. It is also home to Mahakaleshwar Jyotirlinga, one of the twelve Jyotirlinga shrines to the god Shiva.

The earliest references to the city, as Ujjaini, are from the time of the Buddha, when it was the capital of the Avanti Kingdom. Since the 4th century B.C. the city has marked the first meridian of longitude in Hindu geography. It is also reputed to have been the residence of Ashoka (who subsequently became the emperor), when he was the viceroy of the western provinces of the Maurya empire.

In the Post-Mauryan period, the city was ruled by the Sungas and the Satavahanas consecutively. It was contested for a period between the Satavahanas and the Indo-Scythian Sakas, known as Western Satraps; however, following the end of the Satavahana dynasty, the city was retained by the Sakas from the 2nd to the 4th century CE.

Following the conquest of the Sakas by the Guptas, the city soon became an important seat in the annals of that empire. Ujjain is considered to be the traditional capital of King Chandragupta II, also known as Vikramaditya, at whose court the nine poets known as the navaratna (nine jewels) of Sanskrit literature are said to have flourished.