It is our great pleasure to introduce the proceedings of the 20th anniversary edition of the Annual Symposium on Combinatorial Pattern Matching (CPM). The meeting was held in Lille, France, hosted by the Laboratoired'Informatique Fondamentale de Lille (LIFL) a?liated with the Universit e de Lille 1 and the French Centre National de Recherche Scienti?que (CNRS), as well as by INRIA Lille - Nord Europe. Started in 1990as a summer school with about 30 invited participants, CPM quicklyevolvedintoarepresentativeannualinternationalconference.Principally motivated by combinatorial algorithms for...