A Nigantha, follower of Nátaputta. He once visited the Buddha at Nálandá, and there followed a discussion on actions and their efficiency. Díghatapassí reported this discussion to Nátaputta and Upáli, who was listening, went, against the advice of Díghatapassí, to the Buddha and challenged him to a discussion, at the end of which Upáli was converted (M.i.371ff).
The Commentary (MA.ii.594) says that Díghatapassí was long-limbed, hence his name.