Recombinant proteins are proteins that are produced by different genetically modified organisms following insertion of the relevant DNA into their genome. As this recombines the DNA of two different organisms, the word recombinant is used to refer to this process.

Many peptide hormone medications, (including insulin, growth hormone, and oxytocin), and vaccines are the product of recombinant processes. The organism most commonly used is Escherichia coli (E.coli).