This book is a collection of specially-commissioned chapters from philosophers, economists, political and behavioral economists, cognitive and organizational psychologists, computer scientists, sociologists and permutations thereof as befits the polymathic subject of this book: Herbert Simon. The tripartite of the title, Minds, Models and Milieux, connotes the three inextricably linked areas to which Herbert Simon made the most distinguished of contributions. 'Minds' connotes Simon's abiding interest in theorizing human behavior, rationality, and decision-making; 'Models' connotes his extensive computer simulation work in the service of his interest in understanding minds, but also in the service of minds that are situated in a complex social 'Milieux'. This collection while intended to commemorate the centenary of Simon's birth simultaneously offers a timely reassessment of some of his central insights and illustrates the exponentially growing interest in Simon's work from beyond the usual disciplines and constituencies.