Proceedings of the 23rd Workshop on (Constraint) Logic Programming 2009 : [annual meeting of the Society of Logic Programming (GLP e.V.] The workshops on (constraint) logic programming (WLP) are the annual meeting of the Society of Logic Programming (GLP e.V.) and bring together researchers interested in logic programming constraint programming and related areas like databases artificial intelligence and operations research. The 23rd WLP was held in Potsdam at September 15 16 2009. The topics of the presentations of WLP2009 were grouped into the major areas: Databases Answer Set Programming Theory and Practice of Logic Programming as well as Constraints and Constraint Handling Rules.