This presentation is an introduction to JBoss, the most popular Java-based OpenSource application server. JBoss today is used to run one-third of the world's Java EE applications, including a large number of mission-critical systems. We will go through the history, feature set, architectural innovations and vision of JBoss AS, as well as provide references to JBoss deployments. We will conclude the presentation with a discussion of the community build around the JBoss Application Server.