In chemistry, acylation is a broad class of chemical reactions in which an acyl group () is added to a substrate. The compound providing the acyl group is called the acylating agent.  The substrate to be acylated and the product include the following:
*alcohols, esters
*amines, amides
*arenes, ketones
A particularly common type of acylation is acetylation, the addition of the acetyl group. Closely related to acylation is formylation, which employ sources of "HCO in place of "RCO".