An end coupling for a shaft of a rock bolt comprises a body having a lead portion with a leading end, and a tail portion with a trailing end. The tail portion is arranged to be connected to a drive to impart rotation to the coupling about its axis. The body defines a passage extending between the leading and trailing ends and a first portion of the passage extends from the leading end and has a first diameter. A second portion of the passage is disposed adjacent the first portion and has a second diameter that is larger than said first diameter. A first thread extends along at least part of the first portion of the passage and is arranged to engage an external thread on the rock bolt shaft. A rock bolt assembly incorporating the end coupling is also disclosed.