Great Goblin
The Great Goblin is the title of the chief primate of the Church of Gob, the primary religion of the Goblins of the Underkingdoms. The holder of the title is almost always also the King of Greater Siem, the largest and most central of said underkingdoms, and is elected after the death of his predecessor by the Red Masters - almost always from among their own number.
Nominally, all of the underkingdoms are loyal to the Great Goblin in his dual capacities as King of Siem and "Most Magnificent Bishop" of Gob, the Goblin diety. In practice, only the settlements most directly in reach of the Great Goblin's personal armies are loyal in the political sense, and form a state known as Great Siem. The rest of the Underkings are loyal to the Great Goblin only in his religious context, as are the rulers of other Goblin civilizations further afield (and outside the scope of this article).
Interestingly, the position of Great Goblin is not hereditary, because of its status as a church position, and the nominal chastity required of church officials in the Church of Gob would otherwise prevent this - the reality ofter differing widely from this ideal. While a Great Goblin remains the Great Goblin until his death, the position is actually elected by the members of the church heirarchy - usually promoting one of their own to the position.
If you are a goblin lucky enough to be born male and ambitious enough to want to become the Great Goblin, bone up on your skills at court intrigue, make friends with assassins and mercenaries, and always watch your back. To even survive long enough to reach the electing body - the Red Masters - is a testament to your greatness. It is only very rarely a testament that you're favored by Gob - the Red Masters are a self-promoting and insular group, deeply corrupted by avarice and greed, and maintain a faith in Gob only great enough to use the goblin diety's teachings as a lever against the population.