Gajabahu I of Anuradhapura

King of Anuradhapura from c.113 to c.135

Gajabahu I (lit. 'Arm of an elephant'), also known as Gajabahuka Gamani (c. 113 – 135 CE), was a Sinhalese king of Rajarata in Sri Lanka. He is renowned for his military prowess, religious benefactions, extensive involvement in South Indian politics, and for possibly introducing the cult of the goddess Pattini to Sri Lanka. The primary source for his reign is the Mahavamsa, though he is also the only early Sri Lankan king (along with Elara) to be extensively mentioned in the Chera Cilappatikaram (also spelled Silapathikaram).

Next to nothing is known about Gajabahu's youth, except that he was the son of Vankanasika Tissa (reigned 110–113 CE), king of Rajarata from Anuradhapura, and his consort Mahamatta. As such he might have witnessed the most dramatic event of Tissa's reign, the invasion of Rajarata by the Chola king Karikalan. The Mahavamsa mentions Gajabahu's accession and reign of twenty two years and mentions neither Karikalan's invasion nor the military campaigns to south India that Gajabahu became famous for. Instead he is presented as a great patron of religion; the chronicle credits him with the construction of two viharas Matuvihara and Rumika and a stupa called Abhayuttara. Matuvihara was built according to the advice of his Queen mother at the thickest of Kadambha river for honoring her. As well as his Queen mother donated money for the plot of land to build a Vihara for the Great Vihara. He is also credited with making a mantle for Dutugemunu's Mirisavetiya, and for building a reservoir to provide the Abhayagiri monastery with food. He also made improvements to the four entrance ways of the Abhayagiri stupa. He also made tank called Gamanitissa for these Vihara. Apart from that he was to build a hall called Mahejasansala in city. Gajabahu is also credited with the introduction of the cult of the goddess Pattini to Sri Lanka. The Silapathikaram mentions Gajabahu's presence at the consecration of a temple to Kannagi (identified as Pattini in this case) by the Chera king Senguvuttan. However, there is an alternative view that the cult actually arrived in Sri Lanka in the 13th century, and the legend of Gajabahu's patronage was retrospectively created to generate legitimacy for the goddess. The annual Perahara held in Kandy is also thought to have its roots in Gajabahu's reign. Following the successful completion of a campaign into Chola territories the temple of Vishnu in Anuradhapura is said to have staged a procession in thanks, which eventually developed into today's festival. Gajabahu was succeeded by his father in law Mahallaka Naga.

Gajabahu is regarded in modern Sri Lanka as an archetype of the mighty Sinhalese monarch, who avenged humiliation by the Cholas and took the sporadically fought wars between Rajarata and Chola to Indian soil. The Sri Lanka Army has an infantry regiment, Gajaba Regiment, named after the warrior king, and the Sri Lanka Navy had named a ship named after the king, the SLNS Gajabahu. To students of Indian history his reign is important as it provides the 'Gajabahu syncretism' which is used to date many rulers of the ancient Chola and Chera. A stone inscription in Brahmi, dating to Gajabahu I's reign, orders that part of the customs collections at the Godavaya Port at Ambalanthota be donated to the nearby Godapawath Temple. There have been three inscriptions and some 75,000 late Roman coins found in earthen vessels in the region.