Using the thermal oxidation of iron, we show that the growth morphologies of one-dimensional nanostructures of hematite (α-Fe2O3) can be tuned by varying the oxygen gas pressure. It is found that the oxidation at the oxygen gas pressures of ∼0.1 Torr is dominated by the growth of hematite nanobelts, whereas oxidation at pressure near 200 Torr is dominated by the growth of hematite nanowires. Detailed transmission electron microscopy study shows that both the nanobelts and nanowires grow along the direction with a bicrystal structure. It is shown that nanowires are rooted on Fe2O3 grains, whereas nanobelts are originated from the boundaries of Fe2O3 grains. Our results show that oxygen gas pressure can be used to manipulate the Fe2O3/Fe3O4 interfacial reaction, thereby tailoring the oxide growth morphologies via the stress-driven diffusion.