Abstract: The preservation and decomposition of soil organic carbon (SOC) has been the subject of scientific inquiry for decades, owing to its critical role in regulating atmospheric CO₂ concentrations. Iron (Fe) oxides are widely recognized as a rusty sink for carbon (C) because of their large surface area and high adsorption affinity. Fe oxides such as amorphous Fe hydroxides, crystalline Fe hydroxides, and organo-Fe complexes coexist in soils and can be converted to one another. An in-depth understanding of the stabilization of SOC by different types of Fe oxides will strengthen our understanding of soil C cycling. Based on a long-term (25 years) fertilization field experiment in Hengyang, Hunan Province, China, investigations were performed to clarify the stabilization of SOC using different Fe oxides, and its responses to long-term fertilization were discussed. A selective extraction was conducted sequentially to determine the distribution of organic carbon (OC) among different Fe oxides: Na-pyrophosphate (organo-Fe complexes) followed by HCl-hydroxylamine (amorphous Fe hydroxides) and dithionite-HCl (crystalline Fe hydroxides). Ultraviolet and visible light adsorption measurements were used to analyze the composition of Fe oxide-bound OC. The OC contents differed among different Fe oxides in the red soil in the following order: organo-Fe complex-bound OC (2.45–3.59 g∙kg^–1, OC_PP) > crystalline Fe hydroxide-bound OC (1.46–1.51 g∙kg^–1, OC_DH) > amorphous Fe hydroxide-bound OC (0.39–0.70 g∙kg^–1, OC_HH). OC_PP was formed by the coprecipitation/chelation of organo-Fe complexes with low aromaticity, high molecular weight, and high hydrophobicity compounds. OC_HH and OC_DH were primarily formed by Fe hydroxide-adsorbed aromatic compounds. OC_HH had greater average molecular weights and higher aromaticity than OC_DH. Long-term application of chemical fertilizers (NPK) facilitated (P<0.05) the binding of OC with organo-Fe complexes and amorphous Fe hydroxides. However, organic fertilizer (M) addition solely increased (P<0.05) the association of OC with amorphous Fe hydroxides. In addition, NPK treatments increased (P<0.05) the average molecular weights of OC_DH and the hydrophobicity and aromaticity of OC_PP. However, M treatments decreased (P<0.05) the average molecular weights of OC_PP and the hydrophobicity and aromaticity of OC_PP and OC_HH. These findings suggest that long-term fertilization may increase the stabilization of SOC by Fe oxides in red soil; however, the response of SOC stabilization by Fe oxides with varying crystallinity to long-term fertilization is different. In addition, long-term fertilizer addition may change the composition of Fe oxide-bound OC.