Welcome to the 14th International Conference on Principles of Knowledge Representation and Reasoning to be held in Getreidemarkt 9, 1060 Wien, Austria. July 20-24, 2014. Knowledge Representation and Reasoning (KR&R) is a well-established and vibrant field of research. KR&R techniques are key drivers of innovation in computer science, and they have led to significant advances in practical applications in a wide range of areas from Artificial Intelligence to Software Engineering. The underlying approach of explicitly representing knowledge in a tangible form, suitable for processing by dedicated reasoning engines, is a fundamental component of many modern intelligent systems. Foundational and applied research in KR&R contributes to the principles of artificial intelligence. It also contributes to the foundations of longstanding fields including automated planning, databases, and software engineering. In recent years KR&R has also derived challenges from new and emerging fields including the semantic web, computational biology, and the development of software agents. The KR conference series is a leading forum for timely in-depth presentation of progress in the theory and principles underlying the representation and computational management of knowledge. The 2014 edition will be held as part of the Vienna Summer of Logic together with the Federated Conference on Logic, Logic Colloquium and other related events. The Vienna Summer of Logic is expected to be the largest convention in the history of logic.