混合氧化物核燃料（英语：MOX fuel，Mixed oxide fuel）是一种包含有多于一种可发生裂变的物质的氧化物的核燃料，这里的可以发生裂变的物质指的是裂变物质和增殖材料。一般情况下，混合氧化物燃料指的是钚与天然铀、再处理铀或贫铀的混合物。例如，7%的钚与93%的铀的混合物与目前用于大多数核反应堆所使用的低浓缩铀的反应差不多，尽管不是完全一致，但混合氧化物燃料可以作为低浓缩铀的一种替代品。

使用混合氧化物核燃料的优势在于它能够利用武器级钚。武器级钚若不用于制造混合氧化物核燃料，就将会被作为核废料处置，可能会带来核扩散的风险。然而，有人认为随着商用混合氧化物核燃料以及相应的再处理技术的全球化，这将会带来更大的核扩散风险。

Mixed oxide fuel, commonly referred to as MOX fuel, is nuclear fuel that contains more than one oxide of fissile material, usually consisting of plutonium blended with natural uranium, reprocessed uranium, or depleted uranium. MOX fuel is an alternative to the low-enriched uranium (LEU) fuel used in the light water reactors that predominate nuclear power generation. For example, a mixture of 7% plutonium and 93% natural uranium reacts similarly, although not identically, to LEU fuel. MOX usually consists of two phases, UO₂ and PuO₂, and/or a single phase solid solution (U,Pu)O₂. The content of PuO₂ may vary from 1.5 wt.% to 25–30 wt.% depending on the type of nuclear reactor. Although MOX fuel can be used in thermal reactors to provide energy, efficient fission of plutonium in MOX can only be achieved in fast reactors.