  The European Space Agency's Euclid mission is one of the upcoming generation
of large-scale cosmology surveys, which will map the large-scale structure in
the Universe with unprecedented precision. The development and validation of
the SGS pipeline requires state-of-the-art simulations with a high level of
complexity and accuracy that include subtle instrumental features not accounted
for previously as well as faster algorithms for the large-scale production of
the expected Euclid data products. In this paper, we present the Euclid SGS
simulation framework as applied in a large-scale end-to-end simulation exercise
named Science Challenge 8. Our simulation pipeline enables the swift production
of detailed image simulations for the construction and validation of the Euclid
mission during its qualification phase and will serve as a reference throughout
operations. Our end-to-end simulation framework starts with the production of a
large cosmological N-body & mock galaxy catalogue simulation. We perform a
selection of galaxies down to I_E=26 and 28 mag, respectively, for a Euclid
Wide Survey spanning 165 deg^2 and a 1 deg^2 Euclid Deep Survey. We build
realistic stellar density catalogues containing Milky Way-like stars down to
H<26. Using the latest instrumental models for both the Euclid instruments and
spacecraft as well as Euclid-like observing sequences, we emulate with high
fidelity Euclid satellite imaging throughout the mission's lifetime. We present
the SC8 data set consisting of overlapping visible and near-infrared Euclid
Wide Survey and Euclid Deep Survey imaging and low-resolution spectroscopy
along with ground-based. This extensive data set enables end-to-end testing of
the entire ground segment data reduction and science analysis pipeline as well
as the Euclid mission infrastructure, paving the way to future scientific and
technical developments and enhancements.
