Knowledge is a source of intelligence and both knowledge representation and knowledge management are crucial for intelligent systems. Well employed knowledge helps such systems become aware of situations, recognize states and eventually respond to changes. An intelligent system shall incorporate knowledge that helps the system reason about important external and internal factors, and eventually learn from experience and infer missing knowledge. This entry discusses the notion of knowledge and surveys knowledge representation approaches together with concepts and techniques for system intelligence based on knowledge awareness. Moreover, a brief discussion on the author’s view of knowledge representation together with a case study is presented.