Ken Arok (died c. 1227), was the founder and first ruler of Singhasari (also spelled Singosari), a medieval Indianized Hindu–Buddhist kingdom in the East Java area of Indonesia. He is considered the founder of the Rajasa dynasty of the Singhasari and Majapahit line of monarchs. He came from humble origins but subsequently rose to be the most powerful ruler in Java.
According to the Pararaton, a semi-mythical literary work on the kings of Java, Ken Arok was born to a poor peasant family on the bank of the Brantas River in East Java. His mother was the wife of a Brahmin Gajahpura in the kingdom of Kediri. According to the chronicle, the infant Ken Arok was sent down the river by his parents, hoping he would be found by a wealthier family and live a better life. However, the baby Ken Arok was found by a thief called Lembong. His foster father taught him all his criminal skills and young Ken Arok grew to be the most cunning thief in Kediri. Doing much mischief and crimes, he was known all the way to the capital, Tumapel. Many people were sent to catch him, but none were successful. One day, Ken Arok met Mpu Lohgawe, a travelling Hindu monk who patiently taught him to abandon his life as a thief. To persuade him, the monk claimed that he was an avatar of Vishnu, and promised to get him proper work so that he may forget his sinful ways. Ken Arok did not believe the monk one bit, but seeing this as an opportunity to live a more comfortable life, he went along with the monk's plans. Mpu Lohgawe managed to get Ken Arok to become an attendant of Tunggul Ametung, a powerful regional leader of the Tumapel area. Believing this to be a chance to not only get a better life for himself, but for other peasants in the capital, he vowed to rise up the ranks and one day create a kingdom where everyone can live happily, unshackled by poverty.
By chance Ken Arok accidentally saw Ken Dedes, the beautiful wife of Tunggul Ametung, when she was taking a bath. Legend says when the wind blew over her dress and revealed her legs, Ken Arok said that he saw a beautiful light shining. He later told this to his teacher, who stated that it was a sign that Ken Dedes would bear a royal dynasty and any man that took her as wife would be king. Ken Arok, already infatuated by her beauty, became even more eager to take her by any means- including killing Tunggul Ametung if necessary. He convinced himself that this is just another step in his plan to become king and change the world for the better.
Tunggul Ametung however was a very powerful man and held an important position. Thus, Ken Arok needed an exceptionally strong weapon to defeat him, and also had to find a way to do so without himself being punished for the crime. He managed to get this by ordering a kris from a famous smith called Mpu Gandring. However the kris casting took a very long time. After several months, an impatient Ken Arok visited Mpu Gandring to check on the kris' progress. He saw that the kris had already taken shape and was strong enough to be called an exceptional weapon. However, Mpu Gandring stated that he still needed several months to perform rituals to imbue the kris with more magical power, not only to make it strong but also to prevent it from becoming an evil weapon. Ken Arok became furious on hearing this. Knowing that Ken Dedes was pregnant, and determined to murder Tunggul Ametung before his wife gave birth to a possible son and heir, Ken Arok took the kris from its maker and stabbed Mpu Gandring. With his last breath, Mpu Gandring cursed Ken Arok, foretelling that he himself and seven generations of his descendants would be killed by that cursed kris.
Now owning an exceptional weapon, Ken Arok prepared the next step of his plan. He gave the kris to Kebo Ijo, another attendant of Tunggul Ametung. An arrogant and boastful man, Kebo Ijo showed his new kris to everyone he met, all according to Ken Arok's plan. The kris was not only strong, it also had a unique pattern that made it easily recognized. It wasn't long before almost everyone in Tumapel knew about the kris. One night, Ken Arok stole the kris back from Kebo Ijo while he was asleep. He then secretly went to Tunggul Ametung's room and stabbed him to death, and left the kris at the scene. In the morning, everyone in Tumapel was shocked to hear of Tunggul Ametung's death. When they found the kris, they accused Kebo Ijo of being the assassin, just as Ken Arok had planned. Before Kebo Ijo was able to defend himself, Ken Arok stabbed him to death, on the pretext of avenging his master. And so Ken Arok was able to kill Tunggul Ametung, take Ken Dedes to be his wife, and proclaim himself as the new ruler of Tumapel.
Ken Arok's ambition did not stop there. Soon after his ascension, the new king defeated king Kertajaya of the much-larger kingdom of Kediri and founded the kingdom of Singhasari. Remnants of Kediri became a vassal kingdom who served under him. Ken Arok thus founded a new kingdom and started a new dynasty. He took the title Sri Ranggah Rajasa Bhatara Amurwabhumi (The Rainbow King of the Universe and All Lands), and his dynasty was called the Rajasa Dynasty. His new kingdom was centered at Tumapel (which he renamed into Singhasari) about 50 kilometres east of Kediri. To further enforce his rule, he appealed to his people's more superstitious side and claimed to be an avatar of Vishnu and Shiva. For the next few years, Ken Arok's ambition grew; he conquered nearby kingdoms, turning them into vassals, and killed their kings with his kris. As time went on, however, he grew increasingly paranoid of Mpu Gandring's prophecy. Fearing that one day an enemy might take the kris away from him and use it to end his life, Ken Arok hid the kris within the furthest recesses of his palace.
Alas, despite his best efforts, Ken Arok could not avoid the curse. Anusapati, son of Ken Dedes and Tunggul Ametung and thus Ken Arok's stepson, had suspected for a long time that Ken Arok was responsible for his father's death. One day, after finding out the truth, he went after and killed Ken Arok. Legend says that Anusapati used the kris of Mpu Gandring to kill Ken Arok; the same kris that Ken Arok used to kill Tunggul Ametung and thus fulfilling the beginning of Mpu Gandring's curse. Afterwards, Anusapati claimed the throne for himself as the second king of Singhasari, but he too met his end at the hands of the very same kris, wielded by Ken Arok's biological son, Tohjaya. The kris continued to change hands until it fulfilled its intended purpose; killing seven generations of Ken Arok's bloodline.
The kings of Majapahit were believed to be descended from Ken Arok, as also were the Mataram rulers. Ki Ageng Pemanahan, the founder of Mataram, claimed himself to inherit the royal blood of Majapahit. This makes all subsequent Mataram kings descendants of Ken Arok who is also believed to be the ancestor of the new Mataram Empire founded in the 17th century which split into two in 1755 to become the kingdoms of present-day Surakarta, and Ngayogyakarta hadiningrat (The Sultanate of Jogjakarta or Jogja), thus making Ken Arok and Ken Dedes the ancestors of all Javanese monarchs.