  This is a very brief review article, written for a book (in preparation) in
memory of Michael E. Fisher and to celebrate 50+ years since the Wilson-Fisher
renormalization group. Strong-randomness renormalization groups were first
developed to treat various quantum critical ground states, especially in
one-dimensional systems. After briefly reviewing some of the earlier work with
these methods, the recent application of this approach to the many-body
localization (MBL) phase transition is reviewed.
