Rajaraja I (Middle Tamil: Rājarāja Cōḻaṉ; Classical Sanskrit: Rājarāja Śōḷa; 3 November 947 – January/February 1014), also known as Rajaraja the Great, was a Chola emperor who reigned from 985 to 1014. He was known for his conquests of southern India and the Anuradhapura kingdom of Sri Lanka, as well as increasing Chola influence across the Indian Ocean. Rajaraja's birth name is variously given as Arul Mozhi Varman

Rajaraja's empire encompassed vast territories, including regions of the Pandya country, the Chera country, and northern Sri Lanka. He also extended his influence over strategic islands such as Lakshadweep, Thiladhunmadulu atoll, and parts of the Maldives in the Indian Ocean. His conquests were not limited to the south; he also launched successful campaigns against the Western Gangas and the Western Chalukyas, extending Chola authority as far as the Tungabhadra River. In the east, Rajaraja faced fierce opposition from the Telugu Chola king Jata Choda Bhima over control of Vengi. This region held significant strategic importance due to its access to resources and trade routes. The conflict between the two rulers intensified as they vied for dominance in the region, resulting in significant battles and shifting allegiances.

Rajaraja I commissioned the construction of the Rajarajeshwaram Temple in the Chola capital of Thanjavur, revered as one of the most prominent examples of the medieval South Indian architectural style. Additionally, during his reign, important Tamil literary works by poets such as Appar, Sambandar, and Sundarar were gathered and compiled into a single collection known as the Thirumurai. This earned him the title of 'Thirumurai Kanda Cholar' (lit. 'The One Who Found Thirumurai'). He initiated a project of land survey and assessment in 1000 which led to the reorganisation of Tamil country into individual units known as valanadus. Rajaraja died in 1014, and was succeeded by his son Rajendra Chola I.

Rajaraja was the son of the Chola king Parantaka II, also known as Sundara Chola, and his wife Vanavan. As recorded in the Thiruvalangadu copper-plate inscription, his birth name was Arun Mozhi Varman, meaning "The Word of Sun Clan". He was born around 947 during the Tamil month of Aipassi, under the Sadhayam star. The Government of Tamil Nadu recognises his birthdate as 3 November 947. Rajaraja had an elder brother, Aditha II, and an elder sister, Kundavai.

Rajaraja's accession marked the end of a period of competing claims to the Chola throne, following the reign of his great-grandfather Parantaka I. After Parantaka I, his elder son Gandaraditya became king. However, upon Gandaraditya's death, his son Madhurantakan was still a minor, so the throne passed to Parantaka I's younger son, Arinjaya. Arinjaya soon died, and his son Parantaka II (Sundara Chola) succeeded him. It was decided that Sundara Chola would be succeeded by Madhurantakan, likely due to Sundara's preference. However, according to the Thiruvalangadu inscription of Rajaraja's son, Rajendra I, the succession plan may have been made by Rajaraja himself.

Aditha II died under mysterious circumstances, with inscriptions suggesting he may have been assassinated. Shortly afterwards, Sundara Chola also died, enabling Madhurantakan to assume the throne with the title Uttama Chola. Following Uttama Chola's death, Arul Moli Varman ascended the throne in mid-985 and adopted the regnal name Rajaraja, meaning "King among Kings."

When Rajaraja came to power, he inherited a small kingdom centered around the Thanjavur–Tiruchirappalli region, the heart of traditional Chola territory. He transformed this kingdom from one that was recovering from attacks by the Rashtrakuta Empire into one that was a well-organised empire with a powerful army and navy. Under his rule, the northern kingdom of Vengi became closely allied with the Cholas, and their influence expanded along the eastern coast all the way up to Kalinga in the north.

Rajaraja Chola Thiruvalangadu plates states that , Arulmolivarman :