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