A search for direct pair production of supersymmetric top squarks (t˜1) is presented, assuming the t˜1 decays into a top quark and the lightest supersymmetric particle, χ˜01, and that both top quarks decay to purely hadronic final states. A total of 16 (4) events are observed compared to a predicted standard model background of 13.5+3.7−3.6(4.4+1.7−1.3) events in two signal regions based on ∫Ldt=4.7  fb−1 of pp collision data taken at s√=7  TeV with the ATLAS detector at the LHC. An exclusion region in the t˜1 versus χ˜01 mass plane is evaluated: 370<465  GeV is excluded for mχ˜01∼0  GeV while mt˜1=445  GeV is excluded for mχ˜01≤50  GeV.