Suryavarman I (Narvanapala la) was king of the Khmer Empire from 1010 to 1050. After the reign of Udayadityavarman I, which ended around 1000, there was no clear successor. Two kings, Jayaviravarman and Suryavarman I, both claimed the throne. Suryavarman I was a Buddhist who was said in the Chronicles of Chieng Maï to be of Malaysian origin. After nine years of war, Suryavarman I won the throne.

His reign lasted some 40 years and he spent much of that time defending it. Known as the "King of the Just Laws," he consolidated his political power by inviting some four thousand local officials to the royal palace and swear an oath of allegiance to him. Suryavarman I favoured Buddhism but he allowed the people to continue practising Hinduism.

His palace was situated in the vicinity of Angkor Thom, and he was the first of the Khmers rulers to protect his palace with a wall. In 1022 Suryavarman I expanded his territory to the west to Lopburi in Thailand and into Laos.

The major constructions built by this king were the Prasat Preah Vihear, on Dangrek Mountain, and Phimeanakas. Suryavarman I also started the second Angkor reservoir, the West Baray, which is 8 km long and 2.2 km wide. It held more than 123 million liters of water. This is the largest Khmer reservoir that survives.

Suryavarman I died in 1050. He was succeeded by his sons, Udayadityavarman II , who died around 1066 and Harshavarman III (Sadasivapada). The latter continued the struggle against internal rebellions and fought back assaults from the Chams until his death in 1080.