内源性物质，是体内代谢中产生的活性物质及最终产物，比如NH₃、胺类、激素、胆色素、神经递质等都可以称为内源性物质。

Endogenous substances and processes are those that originate from within an organism, tissue, or cell.

Endogenous viral elements (EVEs) are DNA sequences derived from viruses that are ancestrally inserted into the genomes of germ cells. These sequences, which may be fragments of viruses, or entire viral genomes (proviruses), can persist in the germline, being passed on from one generation to the next as host alleles.