  We report the discovery of MASCARA-3b, a hot Jupiter orbiting its bright (V =
8.33) late F-type host every $5.55149\pm 0.00001$ days in an almost circular
orbit ($e = 0.050^{+0.020}_{-0.017}$). This is the fourth exoplanet discovered
with the Multi-site All-Sky CAmeRA (MASCARA), and the first of these that
orbits a late-type star. Follow-up spectroscopic measurements were obtained in
and out of transit with the Hertzsprung SONG telescope. Combining the MASCARA
photometry and SONG radial velocities reveals a radius and mass of $1.36\pm
0.05$ $R_{\text{Jup}}$ and $4.2\pm 0.2$ $M_{\text{Jup}}$. In addition, SONG
spectroscopic transit observations were obtained on two separate nights. From
analyzing the mean out-of-transit broadening function, we obtain $v\sin
i_{\star} = 20.4\pm 0.4$ km s$^{-1}$. In addition, investigating the
Rossiter-McLaughlin effect, as observed in the distortion of the stellar lines
directly and through velocity anomalies, we find the projected obliquity to be
$\lambda = 1.2^{+8.2}_{-7.4}$ deg, which is consistent with alignment.
