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.
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