The super-sized cephalopods live deep in the oceans and are little-known by the scientific community.
An international team of researchers investigated rare samples of the elusive animals' DNA to reveal their family secrets.
They discovered that there is just a single species of squid with no population structure.
The findings are published in the journal Proceedings of the Royal Society B.
The giant squid has been a source of fascination both before and beyond its formal description in 1857 by Danish biologist Japetus Steenstrup.
Its deep-dwelling lifestyle is largely unknown but specimens have been found globally, with the exception of Arctic and Antarctic waters.