Sirius is a process-based crop simulation modeldeveloped in C# for Windows computes. Initially developed for wheat, Sirius has been extended to model inter-plant competition and other species. Sirius is a well validated model and was able to simulate accurately crop growth in a wide range of environments, including Europe, USA, New Zealand and Australia, and for experiments of climate change, e.g. Free-Air Carbon Dioxide Enrichment (FACE) experiments.