[en] We present 44 days of high duty cycle, ultra precise photometry of the 13th magnitude star Kepler-5 (KIC 8191672, T _eff= 6300 K, log g= 4.1), which exhibits periodic transits with a depth of 0.7%. Detailed modeling of the transit is consistent with a planetary companion with an orbital period of 3.548460 ± 0.000032 days and a radius of 1.431^+0.041_-0.052 R _J. Follow-up radial velocity measurements with the Keck HIRES spectrograph on nine separate nights demonstrate that the planet is more than twice as massive as Jupiter with a mass of 2.114^+0.056_-0.059 M _J and a mean density of 0.894 ± 0.079 g cm^-3.