Yamata no Orochi or Orochi translated as Eight-Forked Serpent in English. Similar to the Greek version of hydra.
The Orochi was slain by Susanoo or Susa-no-O a Shinto god of the sea and storms. He got expelled from Heaven for tricking his sister Amaterasu the sun-goddess.After getting expel from Heaven,Susano encounter two "Earthly Deities" near the head of the Hi Rive, now called the Hii River in Izumo Province. They are weeping because they were forced to give the Orochi one of their daughters every year for seven year, and now they must sacrifice their eighth. Susano slays Orochi by firstly preparing 8 refined liquor and let the Orochi get intoxicated with drinking, after drinking, all the heads lay down and slept. Using this chance, Susano cuts the Orochi into pieces, when he cut the middle tail, the edge of his sword broke. It was strange to him, he thrust into and split the flesh with the point of his sword and looked, and there was a sword withing. So he took this sword, and thinking it is a strange thing, he respectfully informed the Heaven. This is the Ame-No-Muraku-no-Tsurugi which is the sword where people call it Kusanagi-No-Tsurugi now.