ISO 31000:2009 Risk Management—Principles and Guidelines. Available from all national and commercial suppliers of ISO standards, such as SAI Global (for Australians).
Australians – check out HB 436 before ordering ISO 31000.
A draft for a revised edition of ISO 31000 is in circulation in early 2017. I downloaded my personal-use copy of the draft from www.iso.org at a cost of $A79.49. Peter Blokland is publishing an analysis of changes on LinkedIn from March 2017.