Giant squid were a species of squid native to Earth.
Jules Verne and the Doctor once encountered Silurians and a giant squid, an encounter which inspired 20,000 Leagues Under the Sea, though the Doctor convinced Jules to remove the Silurians from the story. (PROSE: Peacemaker)
Several giant squid were brought to Delta III along with the Swampies from Delta Magna. One giant squid ate a section of the Key to Time and was mutated into Kroll. (TV: The Power of Kroll)