The two-volume set LNCS 8218 and 8219 includes the peer-reviewed proceedings of the 12th International Semantic Web Conference (ISWC 2013), which took place in October 2013 in Sydney, Australia. This conference is regarded as the leading forum for research in the field of the Semantic Web, where groundbreaking scientific results and technological innovations are presented. The event brings together professionals from various disciplines, including artificial intelligence, databases, social networks, distributed computing, web engineering, information systems, human-computer interaction, natural language processing, and social sciences. Volume 1 (LNCS 8218) contains 45 carefully selected research papers chosen from 210 submissions. Volume 2 (LNCS 8219) includes 16 application-oriented papers accepted from 90 submissions, as well as contributions to evaluations and experiments and works from the doctoral consortium.