The International Year of Astronomy 2009 is supported by eleven Cornerstone projects. These are global programmes of activities centred on a specific theme and are some of the projects that will help to achieve the IYA2009's main goals; whether it is the support and promotion of women in astronomy, the preservation of dark-sky sites around the world or educating and explaining the workings of the Universe to millions, the eleven Cornerstones will be some of the key elements in the success of the IYA2009.

The Cornerstone projects are supported by a number of Special projects, which will develop interactions and link up the different initiatives and projects within IYA2009. These projects provide extra means to achieve the IYA2009's main goals and objectives.