The Euclid spacecraft will have a launch mass of around 2100 kg. It will be about 4.5 metres tall and 3.1 metres in 'diameter' (with appendages stowed). The nominal mission lifetime is five years.

The Euclid spacecraft will be made up of two major assemblies:

the EUCLID payload module consists of a telescope assembly and a set of three scientific instruments, plus other design dependent sub-systems. By definition, the telescope assembly is made up of the optics (mirrors), mechanical structures and mechanisms (cover) shared by all the instruments (before beam splitting). The instruments are dedicated to the physical measurements defined by the science mission case. Depending on the configuration of each channel, they may include fore-optics, mechanisms (e.g wheels, descan mirrors...), micro opto-electro-mechanical systems, detectors and proximity electronics, related mechanical and thermal hardware, and specific data processing units if need be. The payload module interfaces with the service module.

A number of different designs have been produced by industry and institute consortia representing complex mission and system trade-offs, eventually an optical design solution was defined by ESA. This telescope is a modified Korsch with a primary diameter is 1.2 m, and central obscuration 0.4 m.

the service module carries various equipment for the following functional chains: mechanical and thermal, power, command and control, data handling, AOCS. The service module provides the communication links with the ground segment. The Fine Guidance Sensor, whose the optical heads can share the focal plane of one of the instruments of the payload, is functionally attached to the SVM (AOCS).

Two spacecraft concepts have been studied during the assessment phase: one concept from EADS Astrium, and another concept from Thales Alenia Space. They both can be seen on this page.