ThepromiseoftheSemanticWeb,atits most expansive, is to allow knowledge to be freely accessed and exchanged by software. It is now recognized that if the SemanticWebis to containdeepknowledge,theneedfornewrepresentationand reasoning techniques is going to be critical. These techniques need to ?nd the righttrade-o?betweenexpressiveness,scalabilityandrobustnesstodealwiththe inherently incomplete, contradictory and uncertain nature of knowledge on the Web. The International Conference on Web Reasoning and Rule Systems (RR) was founded to address these needs and has grown into a major international forum in this area. The third RR conference was held during October 25–26, 2009 in Chantilly, Virginia, co-located with the International Semantic Web Conference (ISWC 2009). This year 41 papers were submitted from authors in 21 countries. The P- gram Committee performed outstandingly to ensure that each paper submitted to RR 2009 was thoroughly reviewed by at least three referees in a short - riod of time. The resulting conference presented papers of high quality on many of the key issues for reasoning on the Semantic Web. RR 2009 was fortunate to have two distinguished invited speakers. Robert Kowalski, in his talk “- tegrating Logic Programming and Production Systems with Abductive Logic Programming Agents” addressed some of the fundamental considerations - hind reasoning about evolving systems. Benjamin Grossof’s talk “SILK: Higher Level Rules with Defaults and Semantic Scalability” described the design of a major next-generation rule system. The invited tutorial “Uncertainty Reas- ing for the Semantic Web” by Thomas Lukasiewicz provided perspectives on a central issue in this area.