2-Piperidinone (2-piperidone or δ-valerolactam) is an organic compound with the formula (CH2)4CONH. Valerolactam is formed by dehydrogenation of 5-amino-1-pentanol, catalyzed by rhodium and ruthenium complexes, The compound, a colorless solid, is classified as a lactam.

It is the monomer of nylon 5, a polyamide:

n (CH2)4CONH → [HN(CH2)4CO)]n