A Merchant Republic is a realm that can engage in coastal trade. The elected ruler is called a Grand Mayor, Doge (pronounced [ˈdəʊʒ]) or Grand Prince. Muslim trade republics (these must be created, as none exists at any start date) use the Walî Emir title instead of Grand Mayor, and the Walî Malik one instead of Doge.
A Merchant Republic has many unique features compared to a normal republic. Merchant Republics were added in Patch 1.09 and are made playable by 
The Republic DLC. Merchant Republics can be independent, or vassals of a higher-tier liege.
Republics of duchy rank or higher automatically become merchant republics if their capital is a coastal county title at the moment the duchy title is obtained. Thus, a king can create a vassal republic by granting a duchy title to a lord mayor of a coastal county.
The five families
Each Merchant Republic has five leading families, each headed by a Patrician, who vie for control and conduct trading throughout Europe, the Mediterranean and beyond. Each family builds Trade Posts and assembles Trade Zones to build income, and has a Family Palace as its base of operations, complete with levies and the ability to recruit their own retinues. Each Patrician is a vassal to the Merchant Republic, and can conduct warfare and plotting independently of the Doge as well as hold cities and baronies or even their own vassals.
If any one of the five families ever dies out, another family will rise to take its place. This can happen for one of two reasons.
- The last male member of the dynasty dies.
- The patrician ceases to be a vassal of the doge. This can happen if the patrician inherits a higher title than the doge, or if he holds a landed title other than his palace that is then vassalized by another ruler in a war (for example, a county that is conquered by a neighboring duke with the de jure claim on county CB).
Should a merchant house die out, its family palace will be destroyed, its trade posts will be distributed among the other families, and a courtier of the doge, selected according to open elective succession, will found a new family in its place. If playing as a patrician, it is beneficial to repeatedly kill off the other families in order to gradually gather the majority of the republic's trade posts to yourself. If playing as a doge, however, you will only get a trade post if the family has at least four.
Doge election
Doges rule a republic, and since republics elect their leaders, the Doge must be elected. They are not so much elected as chosen, however, from one of the five Patrician families. Each family head has a Respect score below their picture in the Republic screen. The highest score at the current Doge's death wins. The score is affected by age (higher is better) and Prestige. However, if you don't have much of either, then use some wealth (from your trading posts) to start a campaign fund to add to your chances of victory. The Respect score is calculated with the following formula:
[math]\displaystyle{ Respect = Age^2 + (2 \times Prestige) + (5 \times Campaign fund) }[/math]
The campaign fund can be increased or decreased by hitting the plus and minus buttons next to the coins on The Republic screen. While your current Doge is alive, you can always take money out of the campaign fund, but when he dies and your successor takes his place, the money is used up.
For the duration of his reign, the new Doge will receive the capital county, the top-tier Republic title, and any title(s) of the same tier as the Republic title. Furthermore, all vassals that have contracts with these titles are transferred as well.
Effects of dogedom
Being a doge is almost always advantageous. Firstly, you get taxes from your fellow patricians and other vassals (ideally all republics), though not necessarily very much. Also, since you are considered a king (or, as the case may be, a duke or emperor) rather than a baron, it is easier to convince women to marry you and therefore raise the male count (more male family members, more trading posts, more money). Note that you still have to pay the same amount for noble marriages. It also increases dynasty Prestige, which translates into a much easier process to get your son elected Doge (because of starting Prestige). Finally, you are able to declare wars, just like other leaders, including embargo wars against whatever republic is bugging you at the time, while the other patricians can't go to war with you over your trade posts, though you can't go to war with them either.
Laws
King-Tier Merchant Republics may set their own Crown Laws if independent. The highest Crown Authority merchant republics can have is Limited Crown Authority. Doges and Patricians pay taxes at the same rate as burghers, but pay 50% less tax to their liege. Patricians do not benefit from demesne-size increases due to title tiers. A Patrician has a base demesne limit of 1, while being Doge gives a +1 demesne bonus.
Patricians holding onto counties are affected by the succession laws of the counties' de jure kingdom if the kingdom title exists and is not held by their merchant republic. This translates into greater uncertainty as patricians can have their holdings divided up by gavelkind; the holdings may also have a different successor from the one determined by Agnatic Seniority. The minor title of Designated Heir does not overrule the kingdom's succession laws.
Republics and wars
Patricians and Doges build trade posts in any coastal county, as long as it is reachable by sea and not owned by a rival republic. Building trade posts within feudal realms can cause tensions, however. They can declare an Embargo war to raze the trade posts. Doges might approach independent rulers with proposals to ally in an embargo against a competing republic.
A patrician or Doge with a trade post in a county gains a CB to seize a city in that county (as long as the county's owner is not a vassal of the doge's liege). They also gain a CB to claim the county of any city they control, as long as they control a county at most two sea zones away as well.
Additionally, patricians within a Republic can declare war on each other over control of a trade post.
Two Republics can go to war for control of a trade post or a city.
Effects of religions
Any religion can form merchant republics and produce patricians. However:
- Muslim patricians cannot hold mosques in their demesne without penalties. As a trade-off, Muslim patricians are unaffected by decadence, and still retain polygamy. This can make Muslim merchant republics produce more trade posts due to increased numbers of adult males. Muslim trade posts in non-Muslim provinces will also get a + 25% income bonus due to Jizya tax.
- Hindu patricians are still affected by their caste. Patricians following the Indian religions can still take concubines.
- Pagan characters usually start with tribal governments. They cannot convert to merchant republics unless they convert their religion, or reform it. However, pagan courtiers can be invited to your court if you are a pagan yourself (or using favors with the
Conclave DLC), and granted a city, becoming burghers. From there, creating a merchant republic should be easy. Pagan patricians can still take concubines.
Nomenclature
These names are used for merchant republics.
| Shield | Rank | Title | Frame | Ruler | (Latin, Byzantine) | (Muslim) | (German) |
|---|---|---|---|---|---|---|---|
|
Barony | Palace | 
|
Patrician | |||
|
County | Grand City | 
|
Lord Mayor | |||
|
Duchy | Republic | 
|
Grand Mayor | Doge | Wali-Emir | |
|
Kingdom | Most Serene Republic | 
|
Prince Mayor | Serene Doge | Wali-Malik | Merchant League |
|
Empire | Principality | 
|
Grand Prince |
Strategies for doges
Managing patricians
Patricians are essentially useless to you as the Doge:
- They pay no taxes on their trade income
- They only pay half the tax rate of non-patrician vassals on their land holdings
- Powerful, prestigious patricians increase the investment needed to retain the title of Doge
- Their trade posts can block you from adding a particular sea zone to your trade zone(s), and unlike mere patricians, you cannot plot or go to war to gain their trade post
- You can keep them away from crucial areas to some degree by giving them a landed title somewhere else, as for them, the cost of building trade posts is based not on distance to the capital, but the closest landed title.
Therefore, they should be kept as powerless as possible, and ideally destroyed as soon as they have four trade posts. See below.
Patrician dynasties can be kept small by suggesting bad marriages and imprisonment with the Intrigue focus.
Trade posts and family dues
Having extra adult male dynasty members in your court allows you to build additional trade posts. However, these same characters get a share of your monthly income as family dues. Worse, when they die, only half of their wealth can be inherited. There are several approaches to getting the most out of this system.
Exceed your nominal trade post limit:
- Build trade posts during family reunions. Land most of your kinsmen. Ensure they keep breeding (important for republics, theocracies, and eventually for distant relatives). Then, once per generation invite all your kinsmen to your court, build trade posts up to your limit, and get them out of your court again. Try to time each reunion to correspond with winning a holy war, so you can grant the titles you obtained to your family members.
- Kill off patrician families with many trade posts. When a patrician family loses its last male member (e.g. to an assassination spree by you), or its head loses his last landed title (this may be a bug), its trade posts are distributed to the remaining families. As the doge, you will get one if they have at least four. You can then repeat this if the distribution pushes another family to at least four trade posts.
- Steal trade posts from rival republics. You can declare war to seize a single trade post from another merchant republic, even if you are already at or over your trade post limit. This is not very cost-effective unless it causes an additional sea zone to become part of your trade zone(s), but is probably quicker than chain-assassinating patrician families, and can be done relatively frequently (since truces end if any one of the characters that signed the peace dies, and doges usually assume office at middle or advanced age).
Reunite character wealth with the dogedom:
- Nominate a rich successor. Open the "dynasty" page of the ledger and sort by gold.
- Seize wealth from old kinsmen. Use the intrigue focus or excommunication for imprisonment reasons.
Creation of merchant republics
If you are king-level or above, and not a merchant republic yourself, creating vassal merchant republics is a good way to gain money and ships. A merchant republic will form if you grant a county and then a duchy to a coastal mayor.
If you hold a city personally, you can right-click the city to make it the county capital. This lets you choose any courtier you control to be the first doge. You can choose whether to grant the local castle to the doge (he'll pay more in taxes while his family is in power) or arrange for him to have a vassal baron (safer vs factions).
When the lord mayor gains his ducal title, four Patrician families are created automatically and the republic can start creating trade posts. If the doge's dynasty already has a family palace (in an existing republic), the doge does not become a playable patrician and instead an additional minor patrician family is created.
Why create republics?
Upsides to having vassal merchant republics:
- They pay you more taxes than a feudal vassal (very large incomes, taxed at half the republic rate)
- They provide a lot of ships (especially important in early centuries)
- Their trade posts increase the income of nearby coastal cities
- When fortified, the trade posts also protect free loot.
- Patricians may offer to pay you to marry noble women in your court
- No opinion penalty for higher crown authority (without Conclave), restricting vassal wars (with Conclave), or Imperial Administration
- They have their own crown focus, so the capitals are more likely to prosper. (Requires
Reaper's Due)
Downsides:
- They provide few troops compared to feudal vassals
- They can become very powerful if your kingdom is small
- Frequent (due to seniority) and potentially non-dynastic doge succession makes them more difficult to control with non-aggression pacts
- Doges do not approve of your feudal government: -20 "Wrong government type"
- Matrilineal marriages with patrician dynasties are not allowed
Choosing a location
| Prefer... | Reason |
|---|---|
| High "trade practices" technology | More trade posts and more income per trade post |
| A holy-warred duchy | Can grant all the county seats directly to the doge, rather than transferring counts or lord mayors under him |
| A titular duchy, or a duchy which is de jure part of the kingdom where your capital is located. | No vassal king will "desire control" of the republic (once you are emperor). Titular duchies that naturally make good republics are Amalfi in Campania (South Italy) (can only be created by republics); Visby (Gotland) in Sweden; and Socotra near Arabia. However, the de jure duke may be able to destroy the republic with a de jure war, especially while the republic is young. |
| A small duchy | You are limited to 10% of your realm being controlled by vassal burghers, and you may wish to create more vassal republics. Three de jure duchies are a single province: Venice; Genoa in Italy; and Mann in Scotland. |
| A kingdom you will not create | No king will "desire control" or have de jure claims. If you are near your vassal limit, this should be a small to mid-size kingdom (such as Trebizond) or one whose lands you can distribute across other existing vassals. |
| A small kingdom | No king will "desire control" or have de jure claims. If the kingdom existed in the past, you may wish to help the republic create it, lest you be vulnerable to a Liberation revolt. De jure drift can turn titular kingdoms into de jure kingdoms (especially Genoa, Pisa, Cyprus) or shrink existing ones. Lanka (5 coastal / 5 provinces), Brittany (6/6), Aragon (6/6), Wales (7/8), and the many small kingdoms in northwest Iberia. Note that kingdom titles cannot be granted directly to rulers of different government types (though as an emperor, you can still grant a second duchy to a doge and hope he creates the kingdom himself).
Venice, Brittany, Castille, Navarra, Asturias/Léon, and Galicia are all de jure kingdoms consisting of a single duchy. Additionally, the titular kingdom of Cyprus can be created by |
| Not close to other vassal republics | Both merchant republics can build trade posts freely |
| Large, contiguous trade zones create more income | |
| Fewer inter-republic wars | |
| Close to large feudal vassals | Feudal vassals often cannot provide enough ships to transport the troops they provide. You can load the feudal vassal's levies onto the merchant republic's ships. At the same time, the feudal vassals can quickly provide troops to fend off dangers such as marauding Vikings. |
| Near your demesne | Trade zones boost city income and spread technology |
| Outside the de jure kingdom/empire containing your capital | Outlying vassals provide much smaller liege levies, but still pay full taxes |
Choosing a doge
| Prefer... | Reason |
|---|---|
|
Opinion and loyalty |
| Same religion and culture | Opinion and loyalty, carrying over to future generations and all starting patrician families. Can construct trade posts at lower cost. |
| High stewardship | High income on which to pay taxes |
| High demesne limit means more city/castle income can be directly taxed by you | |
| Can be your steward, for an opinion boost, and a chance to fine him for stealing if he is greedy (only without Conclave). | |
| High diplomacy | More taxes from patricians to the doge |
| Can construct trade posts at lower cost | |
|
Adult male courtiers belonging to a patrician's family contribute to trade post limit |
| Has sons under 16 | |
| Major dynasty | New doges will bring gold and sons, and will tend to have more prestige. All of these factors will help them quickly expand the family trade network. |
| This family will win most elections. If you grant the first doge several castles and cities, it's nice to have these settlements paying taxes directly to you. | |
| New doges may bring claims you can press, which is especially useful with Karlings or major infidel dynasties. | |
| Already owns a city | Taxes from this city will flow to you rather than the local count |
| If coastal, expands the region where trade posts can be built cheaply | |
| Existing treasury will help him start a trade network | |
| You can instruct him to marry a specific woman before making him a doge, so he doesn't waste cash chasing prestige |
Choosing a family member will greatly increase your dynasty prestige (seniority succession means many doges), increase the size of your family (thanks to the wine cellar in the family palace), and help you in your own elections. On the other hand, you run the risk that your preferred primary heir—or worse, an ambitious family member with a claim on your primary title—will inherit the patrician palace through its seniority succession.
Keep in mind that each dynasty can only control one family palace. If you try to set up two dynasty members as doges, the second will not become a playable patrician, and will start with five vassal patricians instead of four.