  We report the discovery and characterisation of WASP-180Ab, a hot Jupiter
confirmed by the detection of its Doppler shadow and by measuring its mass
using radial velocities. We find the 0.9 $\pm$ 0.1 $M_{\rm Jup}$, 1.24 $\pm$
0.04 $R_{\rm Jup}$ planet to be in a misaligned, retrograde orbit around an F7
star with $T_{\rm eff}$ = 6500K and a moderate rotation speed of vsini = 19.9
km s$^{-1}$. The host star is the primary of a $V$ = 10.7 binary, where a
secondary separated by 5$''$ ($\sim$1200 AU) contributes $\sim$30% of the
light. WASP-180Ab therefore adds to a small sample of transiting hot Jupiters
known in binary systems. A 4.6-day modulation seen in the WASP data is likely
to be the rotational modulation of the companion star, WASP-180B.
