  The James Webb Space Telescope (JWST) is revolutionizing our view of the
Universe through unprecedented sensitivity and resolution in the infrared, with
some of the largest gains realized at its longest wavelengths. We present the
Systematic Mid-infrared Instrument (MIRI) Legacy Extragalactic Survey (SMILES),
an eight-band MIRI survey with Near-Infrared Spectrograph (NIRSpec)
spectroscopic follow-up in the GOODS-S/HUDF region. SMILES takes full advantage
of MIRI's continuous coverage from $5.6-25.5\,\mu$m over a $\sim34$ arcmin$^2$
area to greatly expand our understanding of the obscured Universe up to cosmic
noon and beyond. This work, together with a companion paper by Rieke et al.,
covers the SMILES science drivers and technical design, early results with
SMILES, data reduction, photometric catalog creation, and the first data
release. As part of the discussion on early results, we additionally present a
high-level science demonstration on how MIRI's wavelength coverage and
resolution will advance our understanding of cosmic dust using the full range
of polycyclic aromatic hydrocarbon (PAH) emission features from $3.3-18\,\mu$m.
Using custom background subtraction, we produce robust reductions of the MIRI
imaging that maximize the depths reached with our modest exposure times
($\sim0.6 - 2.2$ ks per filter). Included in our initial data release are (1)
eight MIRI imaging mosaics reaching depths of $0.2-18\,\mu$Jy ($5\sigma$) and
(2) a $5-25.5\,\mu$m photometric catalog with over 3,000 sources. Building upon
the rich legacy of extensive photometric and spectroscopy coverage of
GOODS-S/HUDF from the X-ray to the radio, SMILES greatly expands our
investigative power in understanding the obscured Universe.
