Platinum catalysts supported onto bayerite alumina were synthesized and studied. Alumina of the θ-Al2O3 type, which was prepared from metallic aluminum by an aluminate method, was used as a support, and platinum(IV) nitrate and hydrogen hexachloroplatinate(IV) precursors containing Pt4+ ions were used for supporting an active component. The catalysts were studied by physicochemical methods such as X-ray phase analysis, X-ray photoelectron spectroscopy, transmission electron microscopy, and ultraviolet-visible diffuse reflection spectroscopy. It was found that platinum occurred in a finely dispersed state in both of the catalysts, and it was uniformly distributed over the support surface. The particle sizes were 2.8 and 0.9 nm in the samples synthesized from platinum(IV) nitrate and hydrogen hexachloroplatinate(IV), respectively. The most uniform surface distribution, high dispersity, and a narrow particle-size distribution were obtained with the use of hydrogen hexachloroplatinate(IV). The catalysts were tested in the partial oxidation of natural gas. The catalyst synthesized using platinum(IV) nitrate afforded an almost thermodynamically equilibrium distribution of the reaction products of partial oxidation at a temperature of 700–800°С.