氢甲酰化反应也称羰基合成，是工业上用烯烃与氢气及一氧化碳在高压（10-100atm）加热（40-200°C）和过渡金属催化下反应制备醛类的方法。反应的总体结果是醛基和氢分别加到烯烃双键的两端，生成增加一个碳的醛的两种异构体的混合物。该法首先由Otto Roelen发现，在化学工业上的应用很广。生成的醛是重要的精细化工产品，可以作为很多产品的合成原料。

该反应的催化剂多为Co、Rh、Ir的配合物，其种类随氢甲酰化反应的进展而发生了很大变化，主要是从最初的四羰基氢钴–经叔膦（如三丁基膦）改性的钴催化剂–铑催化剂（如HRh(CO)(PPh₃)₃）.BASF 使用Co, SHELL使用Co/PR3, UCC使用Rh/PR3, RCH–RP使用Rh/TPPTS. 催化剂Rh相对于Co更好，因为其更高的选择性，以及更好的活性在低压下。目前研究中的多相催化剂。

Hydroformylation, also known as oxo synthesis or oxo process, is an important homogeneously catalyzed industrial process for the production of aldehydes from alkenes. This chemical reaction entails the addition of a formyl group (CHO) and a hydrogen atom to a carbon-carbon double bond. This process has undergone continuous growth since its invention in 1938: Production capacity reached 6.6×10 tons in 1995. It is important because the resulting aldehydes are easily converted into many secondary products. For example, the resulting aldehydes are hydrogenated to alcohols that are converted to plasticizers or detergents. Hydroformylation is also used in speciality chemicals, relevant to the organic synthesis of fragrances and natural products. The development of hydroformylation, which originated within the German coal-based industry, is considered one of the premier achievements of 20th-century industrial chemistry.