WASP-4 is a G-type main-sequence star approximately 891 light-years away in the constellation of Phoenix.

[4][1][2] Despite its advanced age, the star is rotating rapidly, being spun up by the tides raised by a giant planet on a close orbit.

With an orbital period of just 1.3 days it is classified as a hot Jupiter.

[4] The planet's orbital period appears to be decreasing at a rate of 7.33±0.71 milliseconds per year, suggesting that its orbit is decaying, with a decay timescale of 15.77±1.57 million years.

Another superjovian planet in the system is suspected.