We report the discovery and validation of four extrasolar planets hosted by
the nearby, bright, Sun-like (G3V) star HD~108236 using data from the
Transiting Exoplanet Survey Satellite (TESS). We present transit photometry,
reconnaissance and precise Doppler spectroscopy as well as high-resolution
imaging, to validate the planetary nature of the objects transiting HD~108236,
also known as the TESS Object of Interest (TOI) 1233. The innermost planet is a
possibly-rocky super-Earth with a period of $3.79523_{-0.00044}^{+0.00047}$
days and has a radius of $1.586\pm0.098$ $R_\oplus$. The outer planets are
sub-Neptunes, with potential gaseous envelopes, having radii of
$2.068_{-0.091}^{+0.10}$ $R_\oplus$, $2.72\pm0.11$ $R_\oplus$, and
$3.12_{-0.12}^{+0.13}$ $R_\oplus$ and periods of
$6.20370_{-0.00052}^{+0.00064}$ days, $14.17555_{-0.0011}^{+0.00099}$ days, and
$19.5917_{-0.0020}^{+0.0022}$ days, respectively. With V and K$_{\rm s}$
magnitudes of 9.2 and 7.6, respectively, the bright host star makes the
transiting planets favorable targets for mass measurements and, potentially,
for atmospheric characterization via transmission spectroscopy. HD~108236 is
the brightest Sun-like star in the visual (V) band known to host four or more
transiting exoplanets. The discovered planets span a broad range of planetary
radii and equilibrium temperatures, and share a common history of insolation
from a Sun-like star ($R_\star = 0.888 \pm 0.017$ R$_\odot$, $T_{\rm eff} =
5730 \pm 50$ K), making HD 108236 an exciting, opportune cosmic laboratory for
testing models of planet formation and evolution.