The Roman conquest following the two wars with the Dacians did not include the north-west of Romania and therefore neither the region of Oradea, although some historians have claimed at one time this, identifying, in parallel, Oradea with the hypothetical city of Ulpianum. The free Dacians of the present city territory or its vicinity continued to live in their old settlements. Archaeological discoveries belonging to the Free Dacians in the area of Oradea are relatively few, mainly due to the limited archaeological excavations carried out for this purpose. The existing ones, however, show certain influences coming both from the Sarmatian tribes in the immediate vicinity and from Roman influences.

The most consistent information about the history of the city and Bihor during this period comes from the Chronicle of Anonymus, the Chronicle of Simon de Keza, the Register of Oradea, Carmen Miserabile and the Statutes of the Catholic Chapter of Oradea. According to another later source, namely the Vienna Illuminated Chronicle - Chronicon Pictum (written in the second part of the 14th century), King Ladislaus I (1077-1095) "found in the parish of the fortress of Bihor, between the rivers Criș, during a hunt, a place where, at the urging of the angels, he decided to build a monastery in honour of the Virgin Mary, a place he called Varad".

Documented as early as 1113 under the name Civitas Varadiensis in a diploma of the Benedictine abbey of Zobor, Oradea developed over the centuries around its medieval fortress. Oradea was the result of an evolution that spanned a period of several centuries, culminating in the unification of all the settlements around the city (Olosig, Orașul Nou, Subcetate and Velența) into a single nucleus in the mid-19th century. Its development benefited greatly from the construction of the monastery which later became the seat of the chapter (college) of 24 canons.

King St. Ladislaus founded a bishopric here, and more than a century after his death (on 25 July 1095) he was buried in the monastery built by his order in Oradea (around 1134). The consecration of KIng Ladislaus, held on June 27th 1192, marked a rapid rise for the existing ecclesiastical institutions in the city, bringing with it an increase in the social and economic importance of the settlements around the fortress built around the monastery.

An important event for the history of the city was the great Mongol invasion between 1241-1242, when part of the great army of invaders headed towards the Fortress of Oradea, which they would besiege, conquer and burn. The event is quite well known thanks to the writings of the Italian monk Rogerius, present in Oradea at the time, author, later, of Carmen Miserabile (Song of Mourning).

From the end of the 15th century onwards, the town began to receive more privileges from the royalty, which would be consistently reflected in its overall development. The first was the rapid Ottoman incursion on the city on February 7th 1474, when the armies of Ali Oglu Malcovici, the begul of Semendria, attacked Oradea taking advantage of the absence of Matthias Corvinus from the country. As the town had been destroyed to a considerable extent, the king decided to repopulate it and restore it to normality as soon as possible by granting citizens exemptions from customs duty on goods brought to the fair.

The economic development of the city will obviously be accompanied by a flourishing of cultural life, felt especially with the penetration of the first seeds of Humanism and Renaissance. The Italian Renaissance was also greatly encouraged in Oradea by the fact that some bishops and high prelates of the Catholic Church were originally from the Italian peninsula. Of these, Andrea Scolari (1409-1426) was considered to be "a perfect embodiment of the Renaissance spirit". During his episcopate he attracted a large number of Italian artists to the court, built chapels, erected altars, built a space for a library, etc. His rich activity will be successfully continued by his immediate descendants, among whom will be noted John Vitez of Zredna "the most impressive personality of the Renaissance in Central Europe", among others the mentor of the first steps of Matthew Corvinus. He enjoyed the friendship of the great humanist Aeneas Silvio Piccolomini (1405-1464), who became pope as Pius II.

Apart from its cultural prestige, Oradea also became an important scientific centre, as proved, for example, by the erection here by the famous astronomer Georg Puerbach (1423-1461) of an astronomical observatory and the setting of the zero meridian in the Oradea Citadel, on the basis of which he would later calculate the time of the solar and lunar eclipses, recorded in the so-called "tabulas varadienses". A last great bishop of Oradea, before the triumph of the Reformation, was Giorgio Martinuzzi (1534-1551). Serbian on his father's side and Italian on his mother's, he was a great admirer of Renaissance architecture, a particularly energetic and controversial character. His disappearance in 1551 coincided with the end of the period of prosperity that Oradea had known since the second part of the 14th century.

At the beginning of the 16th century, the history of Oradea was marked by the defeat of the Hungarian royal armies at Mohacs by the Ottoman troops, which led to the intensification of the independence of the voivodeship of Transylvania. In 1526, Ferdinand of Habsburg, who was crowned King of Hungary, appointed Ladislaus of Macedonia as Bishop of Oradea. However, he was unable to take office because the town was in the hands of John Zapolya, Ferdinand's competitor. It wasn't until 1528 that the city was conquered by the Imperials, but the city did not surrender. After a decade of disputes, on 24 February 1538, a peace was signed in Oradea between Ferdinand and Zapolya, mediated by Gheorghe Martinuzzi.

Since after 1541, Transylvania became an independent principality, Oradea and Bihor, as well as other western counties, had to choose between joining Ferdinand's Habsburg Hungary or the new principality. If initially, in 1542, in the partial diet of Oradea, they declared their attachment to the Habsburgs, finally, after several prevarications, they finally decided, in 1544, to join Transylvania.

The military operations between 1691-1692 put the town and the surrounding villages under serious strain, causing major damage that the new Austrian administration would hasten to repair. The life of the inhabitants was again seriously affected by the anti-Habsburg movement between 1703-1711, led by Francis Rákóczi II. The villages around the fortress became battlefields between the imperial garrison in the fortress and the rebellious troops, therefore the fortress was subjected to a long siege.

The signing of the peace of Satu Mare in 1711 would also bring recognition by the imperialists of the merits of the people of Oradea in supporting the imperial garrison. Thus, on 27 November 1712 Charles VI signed an imperial decree recognizing the privileges previously granted to the people of Oradea, and also giving them the right to use the city seal and coat of arms. The cessation of armed confrontation led to a sustained development of the economic life of the city, dominated almost equally by agricultural and non-agricultural activities. In fact, a mercurial of 1722 drawn up by the local council of Oradea identified no less than 15 categories of craftsmen. From a cultural point of view, too, a number of advances were recorded, especially in the second part of the 18th century and the first part of the following century. Many of them were due to representatives of the church, among the most representative personalities of this period being the bishops Ignatie Darabant and Samuil Vulcan. In the struggle for political and national rights for the Romanian population of Transylvania, along with other Romanian leaders, Bishop Ignatie Darabant, considered by many scholars as one of the authors of the document Supplex Libellus Valachorum submitted to Emperor Leopold II in March 1791, will also stand out. Behind the scenes, he will also participate in the drafting and submission of the second Supplex, dated 30 March 1792.

The ideas of the Enlightenment would take the form of a constant concern for the organization of a school network as vast as possible and the printing of a large number of books necessary for schools or for the publication of scientific works of general use.

In line with this state of affairs, in the penultimate decade of the eighteenth century in Oradea appeared for the first time a school institution of higher degree, namely the Royal Academy, established following the proposal of December 25th 1776 of the director of the school district of Oradea, Count Károlyi Antal. The actual beginning of the courses will be recorded on November 1st 1780 with a year of philosophy, completed in 1788 with law studies.

The personality who set the lines of development of the spiritual life of Oradea at the beginning of the 19th century was the Greek-Catholic Bishop Samuil Vulcan (1806-1839). He was an energetic follower of the program of establishing new schools and printing a large number of Romanian books at the Buda Printing House, while at the same time setting up a library to collect a large number of works.

In the middle of the 19th century, the four towns around the city (Oradea - Olosig, Oradea - Orașul Nou, Oradea - Subcetate and Oradea - Velența with a total population of 16,849 inhabitants) were unified under a single administration. There is no official act to this effect, but on November 4th, the Habsburg authorities appointed Bölönyi Menyhért as the only mayor of the city. It will reorganise the city's administration, setting up several new institutions. Dissatisfied with his performance, the Austrians replaced him on June 25th 1851 with Csorba János, known for his loyalty to the imperial court and his energy in solving the city's problems.

In the second half of the century Oradea will experience a sustained industrial development. The city's sources of income came from rents on its own premises and houses, from taxes levied on large and medium-sized businesses, and from the customs. In 1899, there were four of the latter: the stone-building customs, the fair customs, the bridge customs and the customs of the floats going down the Criș.

Over the course of the 19th century, the town's population grew from 4,700 in 1814, to 15,727 in 1823, 28,698 in 1870, 31,324 in 1880 and 40,750 in 1890. The growth continued into the next century, with 64,169 inhabitants in 1910 and 69,949 in 1914.

From a political point of view, Oradea has an important place in the events at the end of the First World War, around 1918-1919. On October 12, 1918, the Declaration of Independence of the Romanians of Transylvania, Banat, Crișana and Maramureș was drafted in the house of the lawyer Dr. Aurel Lazăr, a fundamental act for the process of consecration, on December 1st 1918, of the Union of Transylvania, Banat, Crișana and Maramureș with Romania.

On December 7th 1918, the Communists of Oradea organised simultaneously in the main hall of the town hall and in the theatre a rally against the Alba Iulia decision, attended by many demobilised soldiers held in the city at the expense of the town hall. Even more measures were put in place to prevent the Romanian army from entering the city, but the short visit of General Henri Mathias Berhelot on Sunday December 29 greatly raised the morale of the Romanian soldiers. The proclamation in March 1919 of the Soviet Hungarian Republic of Councils and the "proletarian dictatorship" established a state of tension and terror in the city. All persons who endangered the objectives of the government were isolated, a whole series of restrictive measures were taken, and all citizens of the city were forced to work. As the situation in the town had become critical due to the clashes between the "Reds" (communists) and the "Whites" (anti-communists) on April 19-20, 1919, the new town administration led by Mayor Rimler Károly appealed to the Romanian command of the 6th Tileagd Division, asking them to enter the town and establish peace. On the morning of the first day of Easter, 20th of April, the leaders of the city came out to meet the commanders of the Romanian army.

General Traian Moșoiu, accompanied by his senior generals, then entered the town hall building at around 2 pm, thus officially taking over the leadership of the town. Meeting the day after the entry of Romanian troops in Oradea and for the first time in legal and safe conditions, the Romanian National Council of Oradea has moved to take measures of strict necessity for the city, designed to ensure the continuity of social life, order and supply with the necessary daily life. The Romanian administration was introduced in the city from 20th of April, 1919. An important role in this regard being played by Aurel Lazăr, head of the Justice Department in the Sibiu Governing Council. For Oradea, this moment marked the beginning of a new period in its history, the period of integration, in all aspects, into the structures of the Romanian State.

Throughout the interwar period the city's highest administrative authority was the mayor, assisted by a deputy mayor. Decisions taken on behalf of the city were discussed and taken by a deliberative body called the Interim Council from which the Permanent Delegation was appointed. The General Secretariate of the Town Hall had several departments: the administrative, financial, economic, cultural, public education and social welfare departments, the municipal police and the industrial authority, as well as the legal department.

By Royal Decree no. 2465 of September 25,1925, Oradea was declared a municipality, and in 1930 the Heraldic Consultative Commission established the coat of arms of the municipality of Oradea, with the following appearance: on a blue shield with a silver Latin cross held on the left by a winged archangel, nimbed with gold, and on the right by a golden lion, crowned, raised on two paws, with forked tail and red tongue. The shield is stamped by a mural crown with seven towers.

As for the structure of the population by nationality, according to the 1930 census the Romanian population reached 27.7%, the Hungarian 51% and the Jewish 17.7%. Other nationalities, but low in the list, were German, Roma, Ruthenian, Ukrainian, etc.

The intensification of diplomatic pressure from Hungary (supported by Hitler's Germany and Fascist Italy) on Romania in the summer of 1940 and the failure of the bilateral talks in Turnu Severin forced the Romanian side to accept the Vienna Dictate on August 30, on the basis of which the north-western part of Transylvania was ceded to Hungary, comprising a territory of 42243 sq. km with several towns, including Oradea.

The population received the news at 4 pm of the same day through the radio, the news arousing euphoria among Hungarians and despair among Romanians. The next day, Soós István, as a member of the Romanian Parliament, contacted the mayor of the city, Augustin Chirilă, and the prefect Vasile Todoruț. All three agreed that under the new conditions it is vital to maintain peace and order in the city. On September 1st, a large anti-revisionist demonstration took place and moved towards the square and then to the German Consulate in Oradea, where it turned violent and was dispersed by the police.

The events of the summer of 1944 created favourable conditions for Romania to turn its weapons against Germany and liberate north-western Transylvania. Shortly after learning of the new turn that events in Romania had taken after August 23, the Hungarian government took exceptional measures for north-western Transylvania: the area was declared war territory, all demonstrations, public gatherings, etc. were banned. At the end of September Romanian and Soviet troops arrived near Oradea. Moving on from Beiuș, the Tudor Vladimirescu Division passed through Hidișel and Băile Felix, arriving at the city gates on September 27.

Two days earlier, aware of an imminent Romanian-Soviet attack, the Hungarian authorities evacuated the town hall and took refuge outside the city.

The actual liberation of the town was prepared by the heavy fighting that took place in the south of Oradea in the first days of October in the area of Păușa, Leș, Nojorid, Sânnicolau Român, Berechiu and Roit. The decisive attack on Oradea took place on October 12. The Tudor Vladimirescu Division, the 3rd Mountain Division, the Soviet 337th Division and General Pliev's tank and cavalry units participated. On March 11, 1944, the Soviet military administration was installed in the whole of north-western Transylvania, and on March 9, 1945, after the Groza government was installed, the Romanian administration was re-established, thus unfortunately inaugurating the era of Stalinist communism.

Among the achievements of the communist period we should mention the opening of the construction site of the Alumina plant, the opening of numerous light industry enterprises (Solidaritatea, Arta, Crișul, Crișana), the opening of the State Agricultural Enterprises Sere and Avicola, the construction of numerous blocks, hospitals, etc.

Unfortunately, the policy of forced industrialisation also had many negative effects, eventually leading to a real economic crisis - with profound implications in all sectors of public life - with deprivation of all kinds making life difficult for the people who in December 1989 expressed their discontent with widespread protests against the communist regime. The municipal organisation of the National Salvation Front was then formed and took over the leadership of the town.