The Irken Empire consist of a race of insectoid homonid organisms called Irkens. Ever since their home planet of Irk was accidentally almost destroyed by Zim many parts of the race lives on the gigantic ship called The Massive.

Irken society is based on height. The shortest are subjected to harsh labors while the taller Irkens are given easy jobs and are treated with respect. The tallest Irken of each generation becomes the leader no matter their social status or qualifications. This rank is called the Almighty Tallest. If two Irkens of the same generation are the same height they rule together. Such is the case of Tallest Red and Tallest Purple.

The ultimate goal of the Irken Empire is to dominate the universe. They do this by sending a select Irken, who has been given the title Invader, to an enemy planet. Once on the planet they will blend into the inhabitant's society and learn their weaknesses with the help of a Standard Information retrieval or S.I.R Unit. Once the weaknesses are learned the Invader informs the Almighty Tallest and they send the large Armada to wipe out the planet or enslave it.

If the series would have continue, the Almighty Tallest will fall and Zim will take over as leader in the supposed final episode.

Known Irkens