The knowledge society requires life-long learning and flexible learning environments that allow learners to learn whenever they have time, whereever they are, and according to their own needs and background knowledge. In this article, we investigate how Semantic Wikis – a combination of Wiki and Semantic Web technology – can support learners in such flexible learning environments. We first summarise common features of Wikis and Semantic Wikis and then describe different aspects of Semantic Wikis for learning. We also introduce our Semantic Wiki system called IkeWiki and show why it is particularly promising as a learning tool.