A search for resonant diboson production using a data sample corresponding to 4.7  fb−1 of integrated luminosity collected by the ATLAS experiment at the Large Hadron Collider in pp collisions at s√=7  TeV is presented. The search for a narrow resonance in the WW or WZ mass distribution is conducted in a final state with an electron or a muon, missing transverse momentum, and at least two jets. No significant excess is observed and limits are set using three benchmark models: WW resonance masses below 940 and 710 GeV are excluded at 95% confidence level for spin-2 Randall–Sundrum and bulk Randall–Sundrum gravitons, respectively; WZ resonance masses below 950 GeV are excluded at 95% confidence level for a spin-1 extended gauge model W′ boson.