Euclid is an M-Class mission scheduled to launch in 2020, with the aim of constraining the properties of dark matter and dark energy. It will do so by surveying 15000 square degrees of extragalactic sky in order to measure the shapes of more than a billion galaxies and the spectroscopic redshift of 50 millions of star forming galaxies.
The volume of data (raw, auxiliary, reduced), the necessity to combine data obtained in space with ground-based surveys, and the intrinsic complexity of the processing (interdependencies, systematics, quality control) lead to a challenging ground segment organization. 
This talk will address the approach used to design this organization, the structure of the ground segment we have arrived at and the responsibilities of the different sub-entities. Aspects of the development plan will also be presented.