The North Atlantic Treaty Organisation (NATO) was an Earth-based organisation.
In July 1966, NATO was among the computer systems which were to be connected to WOTAN on C-Day on 16 July, an event which was ultimately cancelled following WOTAN's failed attempt to take over London. (TV: The War Machines)
A rogue NATO commander was killed by an Ogri in Little Caldwell. This stopped NATO from discovering that the commander was responsible for abducting both aliens and humans. (PROSE: Return of the Living Dad)
A clone of Martha Jones created by the Sontarans used the memories of her counterpart to access the NATO Defence System and cancel attacks made against the Sontaran ship in orbit above the Earth. (TV: The Poison Sky)
On 25 December 2009, a member of the Master Race transformed from a UNIT officer at UNIT HQ in Geneva had all NATO defenses coordinated and placed under the command of the Master, who ordered missiles launched against the Hesperus. (TV: The End of Time)