次级代谢产物（英语：Secondary metabolites，又称为次生代谢物、二代谢物）是不直接涉及到生命正常生长、发育或繁殖的有机化合物。不像初级代谢产物，缺少次级代谢产物不会导致立即死亡，但是在长期看来，会损伤生物的生存性、繁殖力或美学性，或者一点也没有明显的改变。次级代谢产物常被限定在系统发生学群体中的一个小系列里。次级代谢产物在植物防被食防卫方面起着重要的作用。人类利用次级代谢产物作为药物、调味品或消遣类药物。细菌利用抗生素来和周围的细菌合作和沟通，常常次级代谢都发生在细菌成长期之后的固定期（stationary phase），而人类使用提炼出来的抗生素做药物。

Secondary metabolites are organic compounds that are not directly involved in the normal growth, development, or reproduction of an organism. Unlike primary metabolites, absence of secondary metabolites does not result in immediate death, but rather in long-term impairment of the organism's survivability, fecundity, or aesthetics, or perhaps in no significant change at all. Secondary metabolites are often restricted to a narrow set of species within a phylogenetic group. Secondary metabolites often play an important role in plant defense against herbivory and other interspecies defenses. Humans use secondary metabolites as medicines, flavorings, and recreational drugs.