Greetings Greyfans! Today I'm gonna run down a subject regarding the nation-states of the Flanaess, namely which are theocracies or in other words, realms governed by a (usually) single religion. The aim of this post is to help players and DMs locate a suitable homeland for their devout characters.
The World of Greyhawk is polytheistic overall so there is hundreds of gods and churches everywhere, even Ull. However, some are absolutely ruled by the dominant religion of its populace. For brevity's sake I am not including the jungles of the south or the steppes of the west. These places are certainly inhabited by a pious culture in their own right, but for now we are dealing with the Flanaess proper. Also for ease, I am also going to view these nations as they were in CY 576, the base time of the World of Greyhawk boxed set. Let's have a look:
Theocracy of the Pale (Ruler: Supreme Prelate Ogon Tillit, Cleric 14th of Pholtus) This is the easiest country to spot of course, it has theocracy right there in the name. Nestled in the northeast between mountains and the secular Kingdom of Nyrond, this nation is supremely ruled by the religion of Pholtus, god of light, law, order and the moons. Really, Pholtus wants to be it all and here, from the capital of Wintershiven, the Blinding One is the one and only deity that is real. This is humorous because when Gary Gygax first created D&D he had no established pantheons, but after a while one of the first gods he did name for Greyhawk was indeed, Pholtus. The Pale is a lawful land, nominally lawful neutral to the point of puritanical rule. They hate heretics and don't mind using fire. Your cleric or paladin of Pholtus would do well to start in the Theocracy of the Pale and adventure out to spread the faith with their hymn, "O' Blinding Light".
Grand Theocracy of of Dimre (Bandit Kingdoms) (Ruler: Szek Winvid, Cleric 10th of Pholtus) Oh was one Pholtus theocracy not enough for you? Well then, check out Dimre, an eastern sliver of the "bandit kingdoms" bordering on the Artonsomay River and Phostwood. Dimre was founded by a heretical splinter faction from the Pale whom believe that to understand the light one must walk in the darkness as well. Shady indeed. Needless to say Ogon Tillit hates this domain, as does the folk of Tenh and Nyrond which get raided by the holier than thou bandits. The Theocracy of the Pale has gone as far as sending its own raids into Dimre, but this effort so far has been a stalemate. Players interested in playing a even grittier version of a Pholtus cleric could come from Dimre, if his adventuring mates can stand it.
Prelacy of Almor (Ruler: Prelate Kevont, Cleric 12th of Heironeous) This used to be the western cleric fief of the Great Kingdom of Aerdy. What happened was, while the Great Kingdom got lazy and decadent, Almor prospered under the guidance of Heironeous, god of justice and thus became independent. Having the Kingdom of Nyrond to back you up isn't bad either of course. It's a good, peaceful, pious land, buffering the evil of Aerdy from the west with its noble knights and cavalry. What could go wrong? Players who want a sort of rural, idyllic, free nation to hail from might choose Almor. Oh, and be prepared to defend it.
Caliphate of Ekbir (Ruler: Caliph Xargun, Cleric 16th of Al'Akbar) What survey of theocracies would be complete without a Baklunish nation? The Caliphate of Ekbir on the shores of the Dramidj Ocean is arguably the most holy and good aligned realm in all the World of Greyhawk setting. It is a destination for pilgrims all throughout the west. Ekbir grew from a village of survivors of the Invoked Devastation into a thriving port city, rivaling their ahem less-pious neighbor, the Sultanate of Zeif. While the religion of Al'Akbar, demigod of faith and duty is predominant here, many other deities are openly revered here. Devout to the core, Ekbir is also known for its glorious heavy infantry and impressive war-fleet. If you are looking to make a lawful cleric or paladin from an exotic, "arabian nights" culture, Ekbir is always the best option.
Archclericy of Veluna (Ruler: Canon Hazen, Cleric 19th of Rao) Alright, so if Ekbir or Almor isn't serene enough for your character's background, check out Veluna. This archclericy broke from the vile Great Kingdom long ago with it's much bigger ally, the Kingdom of Furyondy. Veluna is sublimely safe, nestled between good aligned Furyondy, the elves of Highfolk and the gnomes of the Kron Hills. Ruled by the religion of Rao, god of peace and serenity, Veluna has in fact only seen war twice in its 250-year history, once during the Short War and in the famously heroic Battle of Emridy Meadows. Despite the placid, sagely nature of Veluna, Canon Hazen is quite possibly the most powerful cleric in all the Flanaess. Players wanting to serve a high priest representing good morals and not just murder hoboing everything against their god would be advised to consider coming from Veluna.
See of Medegia (Ruler: Holy Censor Spidasa, Cleric 15th of Hextor) Then there is Medegia. The Holy See is the eastern clerical holding of the ever-fracturing Great Kingdom. In the oppressive realm of Medegia, Spidasa and the church of Hextor, god of war is absolute. While this clerical fief has grown rich and autonomous like its good twin, Almor, the Holy Censor still has the ear of the Overking in Rauxes and thus has free reign to do what Hextorians do best, kill stuff. The raiding forces of the See are not well liked among the civilized races of the Grandwood Forest or the Hestmark Highlands. Players wanting to play a grim-dark cleric who serves a sinister, scheming high priest could not do more evil than the See of Medegia.
Iuz (Ruler: Iuz, god of evil, pain, oppression) I was kidding, you can always do more evil in Greyhawk. Should we count the self-titled land of Iuz the Evil as a theocracy? I'm certain it seems to fit. Here we have a literal demigod who is both the absolute ruler and the sole object of worship by his people. This is no mere dictatorial cult of personality, Iuz can back up his claims of godhood with magic and demons summoned from the after-life. His bloody cult is involved in the inner-circle or "government", acting and speaking in his name abroad. So yes, I think the land of Iuz qualifies, even though the numerous humanoids, demons or whatever creatures that inhabit his realm have their own profane patrons. While Iuz is still in power and walks the Oerth his divinity is unchallenged here. Adventurers take note!
What more do you need to know about Iuz and it's cruel, blighted capital, Dorakaa? Well just imagine Mordor from Lord of the Rings with open borders and a lot more magic. Players twisted enough and DMs crazy enough to allow clerics to come from Iuz will undoubtedly be fun to play, if not short lived.
Honorable Mentions. These are not technically theocracies, but they have a pious slant to their culture.
The Shield Lands (Ruler: Holmer of Heironeous, Cleric 7th/Fighter 10th) The valiant, albeit foolhardy Knights of Holy Shielding follow the god of chivalry and justice, acting as the vanguard of good against the evils of Iuz, the Horned Society and the Bandit Kingdoms.
Ket (Ruler: Beygraf Zoltan, Cleric 3rd/Fighter 14th) This Baklunish nation is at a crossroads of many cultures and religions. Indeed, the beygraf is the defender of the "True Faith" and is a cleric in addition to a formidable warrior.
Spindrift Isles (Ruler: Council of Five (elves) and Council of Seven (humans)) There is not much known about these isles saved that the southern isle is exclusively of Suel descent and religion while the northern isles are entirely elven, leaning toward the worship of Sehanine. Trouble is brewing.