Every retelling of the medieval history of San Fermín repeats the same two facts. A relic of the saint arrived in Pamplona in 1186. The church later merged his feast day with a summer cattle fair in 1591. Both facts are true, and both are incomplete. Neither one explains how a city that had no single government, no shared calendar, and three separate armed populations could ever hold one shared festival in the first place. Before Pamplona could have a fiesta, it first had to stop being three cities at war with each other.
That gap matters because it changes what the “medieval roots” of San Fermín actually are. The relic and the calendar merger are religious and administrative footnotes. The real medieval story, the one that explains why Pamplona today functions as a single city capable of throwing one unified festival at all, is a century and a half of civic division that ended in open warfare in 1276 and was only resolved by royal decree in 1423. Skip that story and you are left thinking San Fermín simply appeared. It didn’t. It had to wait for Pamplona to become one Pamplona. That merger is one turning point of four in the full history of Pamplona.
This account draws on the Ayuntamiento de Pamplona’s own municipal history archives, cross-checked against academic material from the Universidad de Navarra and Navarre’s regional historical encyclopedia, rather than the secondhand summaries that circulate in most English-language coverage of the festival.
Three Cities Sharing One Hill
Medieval Pamplona was not one city. It was three, packed onto the same promontory above the Río Arga, each with its own charter, its own mayor, its own flag, and its own defensive walls, functioning less like neighborhoods and more like three independent, hostile townships that happened to share a hilltop.
The Navarrería was the oldest of the three, native-born and built around the cathedral, on the ground once occupied by the Roman city of Pompaelo. Its population was ethnically Navarrese, and its identity was bound up with the diocese and the political power that came with it. Alongside it stood two boroughs founded and populated largely by Frankish merchants and artisans who had migrated south from across the Pyrenees: San Cernin (also called San Saturnino), the commercial engine of the city, and San Nicolás, a second major artisan and mercantile district founded next to it. San Cernin and San Nicolás shared a foreign origin, an entrepreneurial character, and, frequently, open rivalry with each other as well as with the Navarrería.
The Ayuntamiento de Pamplona’s own historical account describes medieval Pamplona plainly as “a mosaic of three differentiated urban centers that coexisted for centuries amid tensions, rivalries, and also exchange.” That mosaic is not a metaphor. Each borough negotiated its own privileges with the crown, policed its own population, and could, and eventually did, take up arms against its neighbors.
The Guerra de la Navarrería: When Pamplona Went to War With Itself
Decades of friction between the three boroughs finally broke into open combat in 1276, in a conflict known as the Guerra de la Navarrería. On one side stood the Navarrería, allied with sections of the Navarrese nobility under García Almoravid and seeking outside support from the neighboring kingdoms of Castile and Aragon. On the other stood San Cernin and San Nicolás, backed by Eustaquio de Beaumarchais, the governor representing the ruling French crown.
The fighting ran from May to September of 1276. San Cernin and San Nicolás won decisively. The Navarrería, the oldest and most historically significant of the three boroughs, was razed. Its population was scattered, and the district sat in ruins for decades, not seeing meaningful reconstruction until 1324, nearly fifty years later.
This is the piece of the medieval story that almost never makes it into festival retellings, and it is documented directly by Pamplona’s city government, not inferred from folklore. It is also the reason the eventual union of the three boroughs was not a bureaucratic formality. It was the resolution of the bloodiest episode in the city’s medieval civic life, negotiated only after the cost of division had already been paid in a burned district and a scattered population.
The Privilegio de la Unión: One City, One Fiesta
Nearly a century and a half after the Navarrería was destroyed, King Carlos III of Navarre, known as Carlos III el Noble, signed the document that finally ended the three-borough system. On September 8, 1423, the Privilegio de la Unión merged the Navarrería, San Cernin, and San Nicolás into a single city of Pamplona, under one town council and one coat of arms. Until that day, as the Ayuntamiento de Pamplona records it, each borough had kept its own flag and its own governor.
The treaty itself runs more than two meters long across twenty-nine chapters and was sworn before the Tres Estados, the assembled knights, prelates, and town representatives of the kingdom. A reproduction is still displayed today in the entrance hall of Pamplona’s City Hall, the same building the encierro route widens past every morning during the modern festival week. Beyond ending separate governance, the privilege also equalized legal rights that had previously varied by borough, certain privileges had existed in San Cernin but not in San Nicolás or the Navarrería, and the crown ordered new walls built around the newly unified city while the old internal walls dividing the three former boroughs were gradually torn down.
Pamplona still marks this exact date. Every September 8, the city holds a medieval market and a joint procession of the Gigantes y Cabezudos through the streets of all three former boroughs, run directly by the Ayuntamiento as an established civic commemoration, a smaller but direct sibling of the more famous July festival.
Two Older Traditions, Finally Able to Merge
Independent of the political story, Pamplona had long run two separate medieval traditions on two separate calendars. Religious ceremonies honoring the saint were held every October 10, his original feast day, following the arrival of his relic from Amiens in 1186. Commercial secular fairs, meanwhile, were held in early summer, when cattle merchants brought livestock into the city to trade. These summer trade fairs are documented from the 14th century onward, entirely separate in purpose and timing from the October religious observance.
Frustrated by consistently poor autumn weather on October 10, Pamplona’s residents eventually secured a change: the saint’s civic feast day moved to July 7, aligning it with the more favorable summer weather of the existing trade fair season. In 1591, the two traditions, the religious feast and the summer fair, were formally combined into a single two-day civic celebration. That merger is the date most historians point to as the true founding moment of the Sanfermines as a unified annual event.
But a unified calendar could only produce a unified festival because Pamplona was, by 1591, already a unified city. Before 1423, any citywide celebration would have needed the cooperation of three separate mayors, three separate charters, and three separate walled perimeters, the exact fault lines that had already produced a war. The medieval roots of San Fermín are not simply a relic and a date change. They are the story of a city that had to stop fighting itself before it could ever throw one shared party.
Walking Three Medieval Cities Today
The three boroughs never fully disappeared. Pamplona’s Old Town, the Casco Viejo, still carries their footprint in its street names and parish churches. The historic churches of San Saturnino and San Nicolás continue to anchor neighborhoods that carry their names, and the Navarrería district around the cathedral remains the oldest section of the city. The entire route of the modern encierro runs through streets that once belonged to these three separate, formerly hostile towns, streets that were unified under a single city government nearly six centuries ago. The route itself has changed over the centuries since, but it still crosses the old borough lines with every step.
Frequently Asked Questions
When did the San Fermín festival originate?
The religious veneration of the saint dates to 1186, when a relic arrived in Pamplona from Amiens. The unified civic festival as celebrated today traces to 1591, when that religious observance was formally merged with an existing summer trade fair and moved to July 7.
What was the Guerra de la Navarrería?
It was a civil conflict fought from May to September 1276 between the Navarrería borough and the allied boroughs of San Cernin and San Nicolás over control of medieval Pamplona. The Navarrería lost and was destroyed, remaining in ruins until reconstruction began in 1324.
Why was medieval Pamplona divided into three separate cities?
The three boroughs, Navarrería, San Cernin, and San Nicolás, developed independently, with Navarrería as the native population center tied to the cathedral and San Cernin and San Nicolás founded by Frankish merchants and artisans. Each negotiated separate charters, privileges, and governance with the crown, which produced ongoing rivalry until their forced merger in 1423.
Why is San Fermín celebrated in July instead of October?
The saint’s original feast day was October 10, but poor autumn weather led Pamplona’s residents to move the civic celebration to July 7 in 1591, aligning it with the more favorable climate of the existing summer trade fair season.
Not every fiesta tradition is this old. The Riau-Riau tradition dates only to 1911, a modern invention next to a festival with medieval roots.
The relic itself belongs to a saint whose own biography is far shakier than this civic history. Pamplona’s city government openly states San Fermín’s story has no confirmed historical basis; the full history of who San Fermín was supposed to be covers that gap in detail.
Every article on the Encierro blog is authored or reviewed by active bull runners with direct experience in Pamplona.