To achieve the demanding aims of XEUS, which involve the detection of sources as faint as 10-18 ergs cm-2s-1 a large x-ray mirror will need to be developed. This core scientific aim implies that the XEUS mirror needs to have an effective collection area at 1 keV of 30 m2 coupled to a spatial resolution on-axis of between 2 and 5 arcsec, so as to avoid source confusion at these very faint flux levels. Finally a field of view of at least 5 arcmin must be covered so as to ensure that a significantly large population of high redshift x-ray sources can be observed in a single pointing over the energy band from 0.05-30 keV. Clearly the key characteristics of XEUS is the large x-ray mirror aperture coupled to the high spatial resolution. The XEUS mirror aperture of 10 m diameter is divided into annuli with each annulus subdivided into sectors. The basic mirror unit therefore consist of a set of heavily stacked thin mirror plates each retaining the correct geometry. This unit is known as a mirror petal and constitutes a complete free-standing calibrated part of the overall XEUS mirror.