In the vicinity of the urban nucleus, are the remains of which was castro of the arévacos, Uxama Argaela; From beginnings of century I a. Of C. this would be transformed into the Roman city of Uxama, nucleus of communications between Asturica Augusta Leon and Caesar Augusta. It was one of the supports in the war of Sertorio against Rome, being destroyed by Pompeyo in 72 a. Of C. In rebuilding it they realized sophisticated works of infrastructure, like the brought of water from the birth of the Ucero river (20 kilometers to the north) by a gallery accessible by people.
From the sixth century the Visigoths called it Oxoma or Osoma. It was an episcopal seat located in the castle grindstone, whose bishop John in 597 attended in Toledo to the twelve Council.
In the tenth century the Arabs, who called it Wasxima, built a watch tower on a bastion of the first wall. In 912 the knight Gonzalo Téllez reconquered it, transferring the town to the neighboring hill, in the left margin of the river Ucero, constructing a castle and walling the locality of Osma. In 939 the king Ramiro II of Leon and the Castilian count Fernán González defeated there caliph Abderraman III; But years later it would be taken up by the Muslims, who used it as a base in the Almanzor rides. Within a short distance, in Calatañazor would be defeated for the first time Almanzor in the year 1000, marking a point of inflection in the war. Count Sancho Garcia would receive it as payment for his services to the Soleyman leader in 1011. In 1088 King Alfonso VI began actively promoting his repopulation, reestablishing the diocese.
Out of the Muslim danger, a part of the population of Osma was established outside the third fortified enclosure, on the right bank of the river Úcero; Around the ruins of a Visigoth church dedicated to St. Michael. In 1101 also was installed there the new bishop of French origin Pedro de Bourges (later canonized like San Pedro de Osma); He took advantage of the foundations of that temple to build a Romanesque cathedral. Underneath was developed the nucleus of artisans and merchants dependent on the bishop, who formed the new Burgo de Osma. Towards 1240 the bishop Juan Domínguez ordered demolishing the Romanesque cathedral and to construct another bigger one in Gothic style.
In the middle of the fifteenth century the bellicose bishop Pedro de Montoya interfered in the internal struggles of Castile, trying to secure his position by building a wall in the Burgo; Of which they remain rest near the door of San Miguel.
In 1469, to the castle of Osma – located on the hill – it approached disguised of merchant Ferdinand the Catholic, when it went to Dueñas and soon to marry in Valladolid with Isabel. A guardian shot a dart with his crossbow, and if it had been successful he would have changed the history of Spain. At the end of century XV the kings granted to him the señorío of Osma to the Duke of Uceda; But this population was losing inhabitants in benefit of the new borough governed directly by the diocese, located in the plain, to the other side of the river. In 1541 the new population gained prestige when the bishop inaugurated the University of Santa Catalina; Extending two centuries more stability and prosperity of El Burgo.
In May 1808 a defense board was appointed in response to the events in Madrid; This caused that in the month of November was assaulted by the French commanded by Marshal Ney, that they sacked it during nine days, arriving to cause a famine. In 1811 the French left there a stable garrison, that was expelled in September of 1812 by the Spanish army.
Although ecclesiastical lordships were repealed in the Cortes of Cadiz, until the confiscation of 1836 lasted the predominance of the bishopric over the region; Being then stripped of his property.
Since the beginning of the thirteenth century, those responsible for the Collegiate Church of St. Peter the Apostle in Soria had been trying to persuade the Popes who deserved to be an episcopal seat. But the success in the management and the influence of the clergy of the Burgo prevented it; Even after the provincial reorganization of 1833, in which Soria was declared provincial capital. The history of Burgo de Osma had to go through until 1959 when concatenates were declared to the two temples of the diocese of Osma – Soria.
Its historical center was declared Historic Artistic Complex in 1993.