A hill near Gayā. Here the Buddha came from Uruvelā after converting the Tebhātika-Jatilā, and here he lived with one thousand monks. On this occasion of his coming he preached the Adittapariyāya Sutta (Vin.i.34f; S.iv.19f; J.i.82; AA.i.57, etc.; PvA.21; Ud.i.9; DhA.i.72).
When Devadatta managed to win over five hundred of the monks to his side, it was to Gayāsīsa that he retired with them, and there it was that the Buddha's Chief Disciples had to go to reclaim them (Vin.ii.199; DhA.i.121; J.i.142, 425, 490f; iv.180). It is said (J.i.185, 508; ii.38f) that Ajātasattu built a special monastery for Devadatta at Gayāsīsa.
The Commentaries (SA.iii.4; UdA.74) say that the hill was so called because it was composed of a flat stone and was shaped like an elephant's head (gaja-sīsa-sadisa-pitthipāsāno). There was room on the rock for one thousand monks.
The hill stands about one mile to the south-west of Gayā and is now called Brahmayoni. To the south-east of the hill Hiouen Thsang saw the three thūpas of the Tebhātika Jatilā (CAGI.524f).
See also Gayā Sutta.