This volume contains the proceedings of the 25th International Conference on Logic Programming (ICLP 2009). The conference took place in Pasadena, Ca- fornia during July 14–17, 2009. The ICLP series of conferences is aimed at p- viding a technical forum for presenting and disseminating innovative research results in the ?eld of logic programming. Theconference,whichwasco-locatedwiththeInternationalJointConference on Arti?cial Intelligence (IJCAI), featured technical presentations, tutorials, - vited talks, and a number of special events, including: – The 5th ICLP Doctoral Student Consortium – The Second Workshop on Answer Set Programming and Other Computing Paradigms (ASPOCP) – The 6th International Workshop on Constraint Handling Rules (CHR) – The 9th International Colloquium on Implementation of Constraint and LOgic Programming Systems (CICLOPS) – The 4th International Workshop on (Constraint) Logic Programming and Software Engineering (CLPSE) – The First Workshop on Commercial Users of Logic Programming (CULP) – Workshop on ISO Prolog — WG17 – The 19th Workshopon Logic-basedmethods in ProgrammingEnvironments (WLPE) Since the ?rst conference held in Marseilles in 1982, ICLP has been the p- miere international conference for disseminating research results in logic p- gramming. The present edition of the conference received 69 submissions in three categories:application, system and tool, and technical papers. From these, the ProgramCommittee selected 29 papers for presentation and inclusion in the proceedings. In addition, the committee selected nine short papers describing on-going research work, PhD theses and research project overviews for poster presentations and inclusion in the proceedings.