John Cairns (1922-) is a microbiologist who pioneered studies in DNA replication. He first came to CSHL in 1960 to work with Al Hershey.
Cairns served as the Director of Cold Sping Harbor Laboratory from 1963 to 1968, overseeing its creation by amalgamation of the Biological Laboratory with the Carnegie Institution's Department of Genetics. Cairns maintained the financial integrity of Cold Spring Harbor at a difficult time in the Lab's history.
In 1968, he chose to step down as director so that he could focus on research, which he continued at Cold Spring Harbor until 1973.