To handle oil spillage and chemical leakage accidents, the development of novel sorbent materials is of global significance for environment and water source protection. In this work, a magnetically carbonaceous fiber (MCF) aerogel was for the first time fabricated by a facile approach from natural cotton as a precursor, and this material can be used as a potential adsorbent without any further chemical modification for oil–water separation under demanding conditions. Owing to its unique and superior properties, such as twisted fiber structure, light weight, high porosity, desirable hydrophobicity, excellent separation efficiency, and strong thermal/mechanical stability, the MCF aerogel exhibits a high adsorption capacity for organic solvents and oils (22–87 times its own weight) and good recyclability. Coupled with the simple, low-cost, and environment-friendly synthesis process, the MCF aerogel will be a promising candidate for removing organic pollutants in environmental pollution cleanup. Hopefully, the MCF aerogel and the corresponding fabrication approach will be further applied to extensive applications including energy storage, fabrication of multifunctional composite materials, and so on.