This paper presents the specification, design, and development of the
Visible Camera (VIS) on the ESA Euclid mission. VIS is a large
optical-band imager with a field of view of 0.54 deg^2 sampled at 0.1"
with an array of 609 Megapixels and spatial resolution of 0.18". It will
be used to survey approximately 14,000 deg^2 of extragalactic sky to
measure the distortion of galaxies in the redshift range z=0.1-1.5
resulting from weak gravitational lensing, one of the two principal
cosmology probes of Euclid. With photometric redshifts, the distribution
of dark matter can be mapped in three dimensions, and, from how this has
changed with look-back time, the nature of dark energy and theories of
gravity can be constrained. The entire VIS focal plane will be
transmitted to provide the largest images of the Universe from space to
date, reaching m_AB>24.5 with S/N >10 in a single broad
I_E~(r+i+z) band over a six year survey. The particularly challenging
aspects of the instrument are the control and calibration of
observational biases, which lead to stringent performance requirements
and calibration regimes. With its combination of spatial resolution,
calibration knowledge, depth, and area covering most of the
extra-Galactic sky, VIS will also provide a legacy data set for many
other fields. This paper discusses the rationale behind the VIS concept
and describes the instrument design and development before reporting the
pre-launch performance derived from ground calibrations and brief
results from the in-orbit commissioning. VIS should reach fainter than
m_AB=25 with S/N>10 for galaxies of full-width half-maximum of 0.3"
in a 1.3" diameter aperture over the Wide Survey, and m_AB>26.4 for a
Deep Survey that will cover more than 50 deg^2. The paper also describes
how VIS works with the other Euclid components of survey, telescope, and
science data processing to extract the cosmological information.