Sri Maharajadiraja Sri Kertanagara Wikrama Dharmatunggadewa, Kritanagara, or Sivabuddha (died 1292), was the last and most important ruler of the Singhasari kingdom of Java, reigning from 1268 to 1292. Under his rule Javanese trade and power developed considerably, reaching the far corners of the Indonesian archipelago.

Kertanagara was the fifth ruler of Singasari and was the son of the previous king, Wisnuwardhana (r. 1248–1268). He effectively held power from 1254 and officially succeeded his father when the latter died in 1268. The Singasari dynasty had come to power in Java following the overthrow of the previous Kediri Kingdom by Ken Arok, the first Singhasari ruler in 1222.

Kertanagara was a follower of a mystical Tantric syncretism of Hinduism and Buddhism, and presented himself as the divine god-king incarnation of Shiva and Buddha. Kertanagara celebrated many religious festivals and commissioned sculptures and metal plaques during his reign.

Singhasari reached the height of its power during Kertanagara's rule, which saw the dramatic expansion of Javanese power into Sumatra, the Malay Peninsula, and Bali. He extended Javanese involvement in the lucrative spice trade with the Maluku Islands. He also put down rebellions in Java by Cayaraja (Bhayaraja) in 1270 and Mahisha Rangkah in 1280.

Kertanagara was the first Javanese ruler with territorial ambitions that extended beyond the island of Java. In 1284, he subjected nearby Bali to vassalage. Kertanagara managed to form an alliance with Champa, another dominant state in Southeast Asia.

Late in his reign, the Pamalayu expedition succeeded in gaining control of the Melayu Kingdom in eastern Sumatra, and possibly also gained control over the Sunda Kingdom and hegemony over the Strait of Malacca. Other areas in Madura Island and Borneo also offered their submission to Kertanagara.

Following the conquest of Song China, the Mongol Yuan dynasty sought to extend its power in Southeast Asia. In 1289 Kublai Khan, the grandson of Genghis Khan, sent his ambassadors to Java, demanding tribute and submission to the Yuan dynasty. Kertanagara took grave offense to the request and arrested the envoys. He branded their faces, cut their ears and sent them back to China with disfigured faces.

Knowing that the Mongols would send a military expedition to punish him, Kertanagara tried to solidify his power. Around 1290, he launched the Pamalayu expedition to Sumatra, to conquer Jambi in the south, one of the successor states to Srivijaya. Jambi was one of the first Indonesian polities where Islam had established its presence, and it already entertained cordial relationships with Yuan China.