This volume contains the proceedings of the 21st International Conference on Logic Programming which was held in Sitges (Barcelona), Spain, from October 2nd to 5th, 2005. The conference was colocated with the International Conf- ence on ConstraintProgramming(CP 2005)and the following 6 post-conference workshops: - CICLOPS 2005: Colloquium on Implementation of Constraint and Logic Programming Systems - CSLP 2005: Constraint Solving and Language Processing - WCB 2005: Constraint Based Methods for Bioinformatics - WLPE 2005: Logic-Based Methods in Programming Environments - MoVeLog 2005: Mobile Code Safety and Program Veri?cation Using C- putational Logic Tools - CHR 2005: Constraint Handling Rules The conferencecoincided with a solareclipse, whichoccurredon October 3rd and was visible in Sitges. No conference activities were scheduled at the time of the eclipse to allow delegates to view this extraordinary astronomical event. Since the ?rst conference that was held in Marseilles in 1982, ICLP has been the premier international conference for presenting research in logic progr- ming.
In this edition of the conference, extra attention was given to novel - plications of logic programming and to work providing novel integrations of di?erent areas. Colocation with CP 2005 further reinforced these themes, as it provided an opportunity for the exchange of ideas and cross-fertilization among two areaswhich havecommon roots. ICLP 2005and CP 2005sharedthe invited speakers to underscore this e?ort. ICLP 2005 broke new ground by holding a doctoral consortium for the ?rst time in the ICLP series of conference.