氢化是一种化工单元过程，是有机物和氢起反应的过程，由于氢不活跃，通常必须有催化剂的存在才能反应。但无机物和氢之间的反应，如氮和氢反应生成氨，一氧化碳和氢反应生成甲醇在化工过程中不叫氢化，而叫“合成”。

氢化在化工生产中一般分为两种：

Hydrogenation – to treat with hydrogen – is a chemical reaction between molecular hydrogen (H₂) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically constitutes the addition of pairs of hydrogen atoms to a molecule, generally an alkene. Catalysts are required for the reaction to be usable; non-catalytic hydrogenation takes place only at very high temperatures. Hydrogenation reduces double and triple bonds in hydrocarbons.