We report the discovery of MASCARA-1 b, the first exoplanet discovered with the Multi-site All-Sky CAmeRA (MASCARA). It is a hot Jupiter orbiting a bright $m_V=8.3$, rapidly rotating ($vsin i_star > 100~rm{km~s}^{-1}$) A8 star with a period of $2.148780pm8times10^{-6} ~rm{days}$. The planet has a mass and radius of $3.7pm0.9~rm{M}_{rm{Jup}}$ and $1.5pm0.3~rm{R}_{rm{Jup}}$, respectively. As with most hot Jupiters transiting early-type stars we find a misalignment between the planet orbital axis and the stellar spin axis, which may be signature of the formation and migration histories of this family of planets. MASCARA-1 b has a mean density of $1.5pm0.9~rm{g~cm^{-3}}$ and an equilibrium temperature of $2570^{+50}_{-30}~rm{K}$, one of the highest temperatures known for a hot Jupiter to date. The system is reminiscent of WASP-33, but the host star lacks apparent delta-scuti variations, making the planet an ideal target for atmospheric characterization. We expect this to be the first of a series of hot Jupiters transiting bright early-type stars that will be discovered by MASCARA.
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