Mahāvaṃsa (Pali: මහාවංස, romanized: Mahāvaṃsa) is the meticulously kept historical chronicle of Sri Lanka until the period of Mahasena of Anuradhapura. It was written in the style of an epic poem written in the Pali language. It relates the history of Sri Lanka from its legendary beginnings up to the reign of Mahasena of Anuradhapura covering the period between the arrival of Prince Vijaya from India in 543 BCE to his reign and later updated by different writers. It was first composed by a Buddhist monk named Mahānāma at the Mahavihāraya Temple in Anuradhapura in the 5th or 6th-century.

The Mahāvaṃsa first came to the attention of Western researchers around 1809, when Sir Alexander Johnston, Chief Justice of the British Ceylon, sent manuscripts of it and other Sri Lankan chronicles (written in mainly Sinhala language being the main language of Sri Lanka) to Europe for translation and publication. Eugène Burnouf produced a Romanized transliteration and translation into Latin in 1826, but these garnered relatively little attention. Working from Johnston's manuscripts, Edward Upham published an English translation in 1833, but it was marked by several errors in translation and interpretation, among them suggesting that the Buddha was born in Sri Lanka and built a monastery atop Adam's Peak. The first printed edition and widely read English translation was published in 1837 by George Turnour, a historian and officer of the Ceylon Civil Service who translated 38 chapters. Louis Corneille Wijesinghe completed the remaining 62 chapters and reviewed Turnour's work, publishing in 1889. A German translation of the Mahavamsa was completed by Wilhelm Geiger in 1912. This was then translated into English by Mabel Haynes Bode, and revised by Geiger.

In 2023, the Mahāvaṃsa was listed an item of globally important documentary heritage on UNESCO’s Memory of the World Programme's International Register.

The Buddhist monks of the Anuradhapura Maha Viharaya maintained chronicles of the island's history starting from the 3rd century BCE. These annals were then combined and compiled into a single document in the 5th century while King Dhatusena was ruling the Anuradhapura Kingdom. It was written based on prior ancient compilations known as the Atthakatha (sometimes Sinhalaatthakatha), which were commentaries written in Sinhala.^{[page needed]} An earlier document known as the Dipavamsa (4th century CE) "Chronicles of the Island" is much simpler and contains less information than the Mahavamsa and was probably compiled using the Atthakatha on the Mahavamsa as well.

Authorship of the Mahavamsa is attributed to an otherwise unknown monk called Mahānāma by the Mahavamsa-tika. Mahānāma is described as residing in a monastery belonging to general Dighasanda and affiliated with the Mahavihara, but no other reliable biographical information is known. Mahānāma introduces the Mahavamsa with a passage that claims that he intends to correct repetitions and shortcomings that afflicted the chronicle compiled by the ancients- this may refer either to the Dipavamsa or to the Sinhala Atthakatha.

The contents of the Mahavamsa can be broadly divided into four categories:

While much of the contents of the Mahavamsa is derived from expansions of the material found in the Dipavamsa, several passages specifically dealing with the Abhayagiri vihara are omitted, suggesting that the Mahavamsa was more specifically associated with the Mahavihara.

A companion volume, the Culavamsa "Lesser Chronicle", compiled by Sinhala monks, covers the period from the 4th century to the British takeover of Sri Lanka in 1815. The Culavamsa was compiled by several authors of different periods.