alpha-Al2O3 powders with three-dimensionally ordered or randomly positioned macropores were synthesized by templating with poly(methyl methacrylate) colloidal crystals. Aluminum nitrate was precipitated with ammonium hydroxide within the interstices of the template; calcination removed the polymer and converted the inorganic precursors into a macroporous skeleton of alpha-Al2O3. Subsequent calcination at higher temperatures and hot stage transmission electron microscopy experiments were performed to study sintering effects on the product morphology. These materials combine the thermal and chemical stability of corundum with a very open structure of uniform macropores that can permit facile transport of guest molecules in potential catalysis, filtration, and sensing applications.