Trishanku was son of Trayyaruni, the king of Ayodhya.

According to an Indian mythological story, he wanted to perform a sacrifice whereby he could bodily ascend to heaven. His priest Vashishtha, however, refused to conduct such a sacrifice, which he said was unauthorized and futile. Vashishtha's sons too declined on the same grounds. But Trishanku turned a deaf ear to their remonstrances. This enraged Vashishtha's sons, who cursed him that he should fall in the social scale and be accounted a pariah.

The king was thus converted into a Chandal and was accordingly forsaken by his kinsmen, ministers and subjects too.

Much agitated at heart over this, the ex-king now approached the sage Vishvamitra, who comforted him, and asking his sons to invite other sages he conducted the sacrifice.

Vashishtha's sons, however, ruled that at a sacrifice commenced by a pariah and conducted by a non-Brahman priest (for such was Vishvamitra till then) no gods would appear. The gods respected this ruling and accordingly no god appeared to accept the offerings. By dint of his own penance Vishvamitra sent Trishanku to heaven, but the gods hurled him down. Exasperated at this Vishvamitra proceeded to create another heaven and began to shape new heavenly bodies. The gods were dismayed at this and sought a conference with Vishvamitra. It was ultimately decided by mutual agreement that Vishvamitra should abandon his plan to create a new heaven and Trishanku should remain hanging in the air. He is still seen in the form of a triple luminary in the heavens. The saliva that dropped from his mouth forms the river Karmanasha, which flows between Varanasi and Bihar and the water of which is considered as ever polluted.