An orbital period of 0.94 days for the hot-Jupiter planet WASP-18b

'Hot Jupiters' abound in lists of known extrasolar planets. Those closest to their parent stars have strong tidal interactions, leading to the suggestion that systems such as OGLE-TR-56 could be used as tests of tidal dissipation theory. Here, the discovery of planet WASP-18b is reported, with an orbital period of 0.94 days and a tidal interaction an order of magnitude stronger than that of OGLE-TR-56b. Either WASP-18 is in a rare, short-lived state, or the tidal dissipation in this system must be weaker than in the Solar System.