The religious head is the character holding the highest position within a religion. The major ones are:
- Roman
: The Pope 
Christianity: The Ecumenical Patriarch
Christianity: The Coptic Pope
Christianity: Patriarch of The East
Islam: The Sunni Caliph
Islam: The Shia Caliph
Unreformed Pagans have no religious head, although they can create one by reforming the religion, called the High Priest or (for 
) Fylkir. Some heresies also have heads, not all of which exist at game start, but can be created by decision, such as the 
Pope. Eastern religions and 
reformed pagans with the Autonomous leadership type also do not have religious heads.
Some religious head titles cannot be destroyed, but are always held by some character; for some heresies, frequently the only character of that religion is its head.
In most religions, the religious head is part of the clergy. In Islam and reformed pagan faiths with the Temporal leadership, he is a noble who often wields considerable secular power. Religious heads may grant divorces, call Crusades, jihads and great holy wars (except Orthodox and Coptic and their heresies), and sanction invasions. The Christian religious heads can also excommunicate members of their church.
Religious heads affect their religions' moral authority in the following ways:
- Their piety (+0.02%/point, maximum +25% MA with 1250 piety; no lower limit for negative piety)
- Their Diplomacy attribute (+0.5%/point)
- +5% MA if they control a temple in the religion's holy sites
- -10% MA if they have the "Immoral Priest" trait
There is also a separate but related concept of a character's religious head, which is not always the same as the religion's head. This is particularly important for Orthodox and Coptic Christianity, which have autocephalous patriarchs; they have limited power compared to other heads. It is also relevant for Catholicism when Antipopes exist.
教廷
The Pope is the head of the Catholic Church, residing in Rome and usually holding the county of Rome itself. His title is king-tier, so he cannot be vassalised except by an emperor and through warfare. The 
Sons of Abraham expansion added a number of unique features to the Papacy.
The Papal States
The Pope also controls a kingdom title with de jure vassals called the Papal States. The pope will be angry with any ruler who control duchies which de jure belong to the Papal States; this is a greater concern to Catholics, who might be excommunicated by the Pope due to low opinion.
Opinion of Bishops towards Pope
Catholic bishops will withhold levies to their secular liege and pay taxes to the Pope/Antipope if they like the Pope/antipope more than their secular liege. If their opinion is +100 to both their secular liege and the Pope/antipope , they will still withhold levies and taxes.
Papal elections
- 主条目：Papal succession
The Pope is elected by the College of Cardinals. In-game, there are nine cardinals at a time, and when the Pope dies, the cardinals elect one among their number to replace him. Vacant cardinal positions are awarded to bishops based on their total suitability score. This is calculated based on the age, traits, culture, and secular power (rank and number of titles held) of the candidate, as well as the Pope's opinion of the bishop's liege. Rulers may invest in a campaign fund to increase the chance that their candidate will be chosen.
The cardinals choose the next Pope based on a similar ranking system, which rulers cannot directly influence. However, Popes who received votes from cardinals from a particular ruler's realm will have a massive +100 relations modifier per vote received.
Papal favors
Catholic leaders in good standing with the Pope can call upon him for special favors. Most of these require the Sons of Abraham DLC; the exceptions are divorce, excommunication and invasion. Most favors reduce the Pope's opinion of you (for 20 years). The piety costs of papal favors are halved if your primary title has papal investiture.
| Favor | Cost | Opinion | Comments |
|---|---|---|---|
| Ask to nominate bishop | 50 gold 30 piety |
Primary title must have papal investiture. | |
| Ask for divorce | 100 piety | -5 | Spouse's family unhappy. In the case of spousal infidelity, the religious head always accepts, the piety cost is waived, and there is no penalty to religious head opinion. Less likely to be accepted if target is same dynasty as Pope. |
| Ask for claim | 100 piety | -10 | You can request a claim on a county or duchy by pressing the "Claim" button on its title screen or by right-clicking its ruler. A button under the Pope opens a list of claims he is willing to give. Not usable on titles held by clergy, burghers, or patricians. Unless you are asking the real Pope, target must have the same religious head. More likely to be accepted if the target is excommunicated. |
| Ask for excommunication | 100 piety | -15 | Moral authority > 40%. Same religious head. |
| Ask to lift excommunication | 50 piety | -15 | More likely to be accepted if target is same dynasty as Pope. If you are excommunicated, use "Repent Sins" instead. |
| Ask for money | 100 piety | -25 | Gives double ruler's annual income. |
| Ask for invasion | 500 piety | -50 | Gives you a Sanctioned Invasion CB, which you do not have to use immediately. Moral authority > 50% |
| Ask for crusade | 500 piety | -100 | See Requesting a crusade for all requirements. Moral authority > 5% |
Antipopes
- 主条目：Antipope
Antipopes are a special feature of Catholicism. They are bishops controlled by a ruler, and hold a rival claim to the papacy.
Heretic Popes
If the Sons of Abraham DLC is active and Rome is held by a Fraticelli ruler, that ruler can, by decision, create the Fraticelli Papacy for a cost of 1000 piety. The Fraticelli religion works just like Catholicism, except that the Fraticelli Pope is duke-tier instead of king-tier.
牧首
- 主条目：Autocephaly
Some Christian religions have a feature called autocephaly with intermediate religious heads called Patriarchs, autonomous in their jurisdiction, but reporting to an overall head.
The following religions use autocephaly and have the associated overall religious head:
- Orthodox: The Ecumenical Patriarch (usually in Constantinople)
Iconoclast: The Iconoclast Patriarch (in Constantinople, if formed)- Monothelite: The Monothelite Patriarch (usually in Antioch)
- Paulican: The Paulican Patriarch (usually in Constantinople)
- Miaphysite: The Coptic Pope (usually in Alexandria)
Monophysite: The Monophysite Pope (usually in Alexandria)
These always exist, except that no one holds the Iconoclast Patriarchate initially; if you have the Sons of Abraham DLC, the Iconoclast Patriarch can be created decision by the liege of the Bishop/Patriarch of Constantinople if both are Iconoclast.
One exception is in 
769, where the nobles and Baselius of the Byzantine Empire are Iconoclast, where Constantinople (the bishopric) is held by the Iconoclast Patriarch. However, any Byzantine Emperor who is not 
can denounce Iconoclasty, converting him and the Patriarch to Orthodoxy (destroying the Iconoclast Patriarchy and granting him the Ecumenical Patriarchy in the process). Until this decision is taken, the Ecumenical Patriarchate does not exist.
Another exception is when the title is destroyed using a CB that destroys titles, such as the Tribal Invasion CB. The Ecumenical Patriarchy can still be restored via a decision, provided an Orthodox ruler controls Constantinople. This will grant both the bishopric and the top level holding of Constantinople to the new Patriarch, and grant him independence.
The Ecumenical Patriarchate is king-tier, and is usually the Byzantine Emperor's vassal and religious head (so he cannot appoint an autocephalous patriarch, but he has all the benefits of one); the rest are duke-tier.
The Orthodox heresy Bogomilism and the Nestorian heresy Messalian have no head.
Mechanics
The Patriarchate has a unique mechanic of usurping their capital barony. The only requirement for this is that the bishopric in question is held by a character of the same religion as their head.
Upon doing so:
- they will receive the barony in question
- if the barony was the capital of a county, they will obtain the county title and all other baronies associated with it
- will become the vassal of the lowest-ranked ruler that can vassalize them
An example of the above: The Bishopric of Alexandria is currently held by a Coptic character. His lieges are, in order, the Count of Alexandria, the Duke of Alexandria, the King of Egypt, and the Emperor of Arabia, all different characters. (Their religion does not matter.) Once the Coptic Pope usurps the Bishopric of Alexandria from the current Bishop, he will become a vassal - however because Counts and Dukes cannot hold Dukes as vassals, he breaks the vassal contract with the Count of Alexandria and Duke of Alexandria and becomes the direct vassal of the King of Egypt, and consequently an indirect vassal of the Emperor of Arabia.
In a similar example with the Ecumenical Patriarch and Constantinople, he would instead be the direct vassal of the Emperor of Byzantium instead of the King of Greece, as Kings cannot vassalize Kings.
Mending the Great Schism
The 
Legacy of Rome DLC is required for this decision.
If all five seats of the pentarchy (Constantinople, Rome, Jerusalem, Alexandria, and Antioch) are controlled by Orthodox bishops who are all, along with the religious head, vassals (direct or indirect) of an independent ruler of the same religion, this liege has a decision to mend the Great Schism. This gives all Catholic characters the opportunity to convert to Orthodoxy and makes Catholicism and its heresies into heresies of Orthodoxy. This will not happen to Miaphysitism or Nestorianism, however, likely because these branches of Christianity broke off before the Great Schism.
Iconoclasts, Paulicians, and Monothelites can also mend the schism if one of these heresies manages to replace Orthodoxy as the parent religion. Bogomilists, having no religious head, cannot mend the schism. Miaphysites, Nestorians, and their heresies, though they use the same mechanics as Orthodoxy, cannot mend the schism either.
Even though the Iconoclast, Paulician, and Monothelite Patriarchs can mend the Schism if they are orthodox, the Schism cannot be mended if the Pope (the bishop of Rome) has abandoned the Catholic faith for the Cathar, Fraticelli, Lollard or Waldensian heresies.
Caliphates
A Muslim religious head is known as a Caliph, a political and religious successor to the prophet Mohammad. Unlike Papacies and Patriarchates, which mainly hold religious authority and are usually regional secular powers at best, caliphates are often large feudal lands ruled by noble lords. This means one can play as the Caliph and call Jihads against enemy religions.
Caliphates are strongly tied to the primary title:
- When the primary title of a secular religious head is usurped, the religious head title is usurped as well. For example, taking the Arabian Empire may also make you the Sunni Caliph, as long as you are also Sunni.
- Characters of other religions are disqualified from the ruler's succession.
- Caliphates are destroyed if their holder becomes unlanded.
Abilities of caliphs
Muslim religious heads (including the Yazidi and Hurufi Sheikhs) gain access to two powerful CBs. You can use Caliphal Subjugation to take Kingdom-tier territories from rulers of the same religion, so long as you either border the kingdom or own land in it. (You retain the Muslim Invasion CB against everyone else.) You also have the ability to call Jihads every 30 years, which (upon success) both increase your religion's Moral Authority and potentially give you large amounts of land.
The disadvantages of being Caliph are minor. Your character's Diplomacy and Piety count for your religion's Moral Authority; if your character is impious or antisocial, you may have a hard time converting provinces, and heretics will pop up more often. The Caliphate or Sheikhdom counts as a duchy title, discouraging you from holding two de jure duchies. If your diplomacy and intrigue are both very low, you may be at risk of becoming known as a Wicked Caliph 
, which lowers moral authority. You also do not have access to the Give Sadaqah decision.
Creating a caliphate
A Muslim ruler who meets special requirements can create a caliphate for their branch of Islam.
- No caliph exists for this branch of Islam.
- Independent, or all lieges follow the same branch of Islam.
- For Shia: there is not an ongoing Shia caliphate revolt.
- For Shia, Sunni, Ibadi, or Hurufi:
- For Yazidi:
- 1000 Piety
- Control Mosul
- For Kharijite:
- 1000 Piety
- (Control Mecca and Medina) OR (control Jerusalem, Damascus, and Baghdad)
Players who meet all requirements will see a Title can be created alert. Players who are unsure which requirements are unmet can open the Religion tab, click the crown icon under "No Head", and hover the "Create Title" button.
Getting the Sayyid trait into a dynasty without Ruler Designer requires matrilineal marriage. This is difficult because Muslims normally cannot marry matrilineally nor suggest matrilineal marriages. With 
Conclave DLC, matrilineal marriage becomes possible if you reach at least Notable Status of Women and then switch to a non-agnatic form of succession.
Judaism
A Jew who restores the Kingdom of Israel and has built the Third Temple can, by decision, reinstate the office of Kohen Gadol, or High Priest. Like the Zoroastrian religious leader, the Kohen Gadol can call Great Holy Wars as soon as his office is reinstated.
Zoroastrianism
With 
The Old Gods DLC, Zoroastrians can restore their ancient religion to prominence by retaking the Persian Empire and appointing a Moabadan-Moabad (Priest of Priests) who will function thereafter as a religious head. A notable feature of the Moabadan-Moabad is his ability to call Great Holy Wars without having to wait until the 11th or 12th century like Christians, Muslims or Reformed Pagans.
Reforming Pagan Religions (Without Holy Fury)
It is also possible with The Old Gods DLC to reform Pagan religions. The ruler who forms it and his direct vassals, demense, and courtiers will automatically convert, while other rulers have the option of conversion. This has the following effects:
- The old, unreformed religion has "old" in front of it, showing that it's the unreformed version, e.g. "Old Tengri". The old religion also becomes a heresy of the reformed religion.
- The religion becomes organised, getting a permanent +20% moral authority, which makes conversion of others easier and makes them less prone to conversion to other religions.
- The religion gets a head. This is a duke-tier vassal like an Orthodox Patriarch, except the Germanic Fylkir who is a secular ruler like the Muslim Caliphs. The leader can call Great Holy Wars (which are Crusades with a different name), so long as either the Christian Crusades or the Muslim Jihads are unlocked. Once a Great Holy War has been unlocked for one Pagan type, they are unlocked for all Pagan types.
- If the Player has the relevant DLC, the reformed faith gets a Holy Order. The Germanic Jomsvikings require The Old Gods, the Zunist Sun Warriors require Charlemagne, and all others require Sons of Abraham. (Note that the Jomsvikings may form on their own after the year 920, even if the faith is not reformed.)
- Rulers gain access to a modified Holy War casus belli, requiring 100 piety but having only a 5 year truce and usable against anyone of a different religion, including reformed and unreformed Pagans of a different religion.
- Rulers lose access to the Subjugation casus belli.
- Religions that get a defensive attrition bonus (all but Tengri and Aztec) lose it, but holdings keep their levy/garrison size and strength bonuses.
- (Without Conclave) Feudal rulers may set Crown Authority higher than Low.
- Tribal Pagan rulers do not receive opinion penalties from Reformed Pagan vassals, can have Gavelkind succession (along with Elective Gavelkind), and may settle to either feudalism or a Merchant Republic so long as they meet other requirements.
- Feudal rulers may use succession laws other than gavelkind (and ultimogeniture for Mongols), so long as they meet other requirements.
- Independence wars no longer have increased ticking warscore, making them harder to win. This is bad for vassals, but good for rulers.
- The "short reign" opinion penalty returns to its normal level (50% higher than other religions when unreformed).
- Germanic, Tengri, and Aztec rulers lose the prestige penalties for being at peace, but gain the usual opinion penalties for raising vassal levies.
It is possible to reform any of the Pagan religions except the generic Pagan and Hellenic religions. This requires 750 piety and either owning all five Holy Sites or owning three and having 50% moral authority.
Without Holy Fury, pagan reformation always creates a duke-tier religious head.
Reforming Pagan Religions (With Holy Fury)
With Holy Fury, in order for the reformed pagan faith to have a religious head, the Leadership type chosen by the reformer must not be Autonomous. Also, with Holy Fury, Hellenism and the Bon faith can be reformed. The nature of the religious head depends on the leadership type.
Note that with Temporal, you cannot hold Temples without penalty unless you are reformed Bon with Monastic Feudalism. Temporal leadership also means that you are encouraged to act in a pious manner, as your piety and traits directly affect the Moral Authority of the faith.