Inspired by the versatile oxidation chemistry catalyzed by nonheme iron enzymes, we have been investigating the iron-catalyzed oxidations of hydrocarbons. Highly stereoselective cis-dihydroxylation of olefins have been observed with the use of nonheme iron(II) complexes with H2O2 as oxidant. Insights into the catalytic mechanism have been obtained from a combination of product distribution studies, 18O labeling experiments, and kinetic analysis as well as DFT calculations. These results implicate a high-valent iron-based oxidant. Hydrocarbon oxidation can also be observed for iron complexes supported by tris(pyrazolyl)borate ligands that activate O2. A high-valent iron-based oxidant is also postulated for these reactions, which exhibit shape selectivity. The unusual shape selectivity observed suggests that substrate recognition can be elicited even in a biomimetic complex of relatively simple design.