We report the discovery of HAT-P-30b, a transiting exoplanet orbiting the V = 10.419 dwarf star GSC 0208-00722. The planet has a period P = 2.810595 ? 0.000005 days, transit epoch Tc = 2455456.46561 ? 0.00037 (BJD), and transit duration 0.0887 ? 0.0015 days. The host star has a mass of 1.24 ? 0.04 M , radius of 1.21 ? 0.05 R , effective temperature of 6304 ? 88 K, and metallicity Fe/H = +0.13 ? 0.08. The planetary companion has a mass of 0.711 ? 0.028 M J and radius of 1.340 ? 0.065 R J yielding a mean density of 0.37 ? 0.05 g cm--3. We also present radial velocity measurements that were obtained throughout a transit that exhibit the Rossiter-McLaughlin effect. By modeling this effect, we measure an angle of Delta *l = 735 ? 90 between the sky projections of the planet's orbit normal and the star's spin axis. HAT-P-30b represents another example of a close-in planet on a highly tilted orbit, and conforms to the previously noted pattern that tilted orbits are more common around stars with T eff 6250 K.