The first known mention of Eisenstadt in an official document dates back to the year 1264.

The Latin document mentions a "Capella sancti Martini de minore Mortin", that is a chapel consecrated to St. Martin in "Little Martin", or as it was called later in German "little Mertesdorff". It was a small village of little interest that probably consisted of said chapel and a few houses. At the end of the 13th until about the middle of the 14th century the city was owned by the Gut-Keled family and called Mortunzzabou in 1296, Zabemortun in 1300. 

A document signed by King Louis dating back to 1371 mentions Eisenstadt as part of the reign Hornstein. The city's owners, the Kanizsai family, had the city fortified with a strong wall and got royal permission to do so in that year (" villa seu oppidum Zabamortum"). At the same time they built a new fortress and thus the foundations for the later development of the city. 

Due to the fact that the village was surrounded by a strong wall, it was said to be impregnable. It was called "iron" or the "iron city". And thus it was later called Eisenstadt, the iron city.

Eisenstadt is built on ancient settlement grounds

Numerous prehistoric finds proof that the area known as Burgstallberg has already been settled during the Hallstatt Period. Later the area was settled by Romans and Celts. The former Roman settlement was located around the grounds of the Martin's Barracks and - as countless finds show - was rather large. During the times of the Germanic Migration the area was settled by Huns and many Germanic tribes. Until around 568 the area was inhabited by Langobards, then by Awars. During the Carolingian Ostmark (Eastern Border, around 800 C.E.) the Bayers began living in the region, and they stayed on after successfully defeating the Hungarians.

The settlement first appeared in the annals of history in 1118 as "castrum ferreum". The first certain written mention goes back to the year 1264, in which Eisenstadt was mentioned under the name "minor Mortin". 

In 1300 Eisenstadt was called "Zabemortun". The word "zabe" is thought to go back to the Hungarian word "szabad" (=free). This probably indicates that "Mortun" (Klein-Martinsdorf) already was endowed with certain special rights and was most likely used as market place.

In 1373 "Eysenstat" was bestowed city rights.

In 1388 the city received market rights. It was at this time that the Kanizsai family saw to it that the city was surrounded by strong fortifications and they also had a water fortress built inside these city walls. 
1440/45 the Kanizsai lost Eisenstadt; it was pawned off to Duke Albrecht VI. 
The Peace of Bratislava (1491) brought Eisenstadt under Austrian administration for about 150 years and in the following decades it was pawned off to different Austrian noble families.

In 1529 and 1532 the Ottomans occupied Eisenstadt while they were headed for Vienna. After this occupation, the city walls were improved and bastions were added.
In 1530 the Reformations swept over the city and by the middle of the 16th century the majority of the population had become Lutheran. 
In 1585 the Viennese court organised a counter-reformation. 
In 1589 an immense fire destroyed the better part of the city.

When the reigns Forchtenstein and Eisenstadt were pawned off to Nikolaus Esterházy in 1622, a name appears on the political and historic landscape that was to have a decisive influence on the city for the next 300 years.

When the pawned off regions in Western Hungary were supposed to be returned to the Empire in 1648, the city of Eisenstadt managed to buy itself the status of a royal free town. Mayor Paul Eisforth organised the payment: 16,000 florin and 3,000 buckets of wine (worth around 9,000 florin).

In 1671 the Jews of Eisenstadt were moved into an area known as Unterberg. The ghetto formed a separate community here. In 1674 the hospital was founded and in 1701 construction began on the so-called Bergkirche, later also known as Haydn-Church. Artisans started settling the area around the building site. They were later followed by employees of the princes and artists. The Oberberg community was formed.

In 1704 and in 1706 the Kuruzzen tribe occupied Eisenstadt.

At two occasions, in 1704 and in 1706 the Kuruzzen tribe occupied Eisenstadt. After devastating fires in 1768 and 1776 the city centre was rebuilt. The blossoming burgher culture was reflected in the two and three storey houses with gothic ceilings and baroque facades. They also incorporated middle-aged building elements such as the old city walls and the powder tower, which went well with the overall architecture of the city. The city could be seen from miles away because the church consecrated to St. Martin was an immense landmark. 
By and large the appearance of the city has remained the same to this day. 

In 1713 the Black Plague ravaged the city and killed many; among its victims was also Prince Paul Esterházy.

1761 Appointment of Joseph Haydn

Under the reign of the princes Nikolaus I. and Nikolaus II. the city saw one of its most glorious eras in history. In 1809 Eisenstadt was occupied by French troops. In 1813 the house Esterházy was heavily indebted, which forced them to set up austerity measures. The arts are generally the first to go in times of need, and so it was for the Esterházy family, too: the famous court musicians were let go. This marked the end of the blistering style of holding court the Esterházy family had been known for.

The jumble of events during the revolutionary year 1761 was also an important year in the city's history: Joseph Haydn became vice conductor of the court musicians. A chapter was written in music history that led Eisenstadt to fame. It became known as centre of musical excellence around the globe.1848 only marginally touched Eisenstadt. 1853 construction began on a cadet school at the edge of Eisenstadt. 1876 Eisenstadt lost all its old special rights within the framework of a Hungarian constitutional reform and was put under the administration of a Comitat as "city with regular magistrate". In 1897 a railway was built between Bratislava and Sopron, a line which also connected Eisenstadt to the railway network.

In 1918 after the end of the WW1 and the decline of the Danube Monarchy Eisenstadt faced an important decision: it had to decide wether it wanted to belong to Austria or Hungary.

On 28th of August 1921

After a three-year struggle, on 28 Aug 1921, Burgenland was to become part of Austria in accordance with the respective peace treaties of St. Germain. After a popular vote in 1922 decided that Sopron would remain part of Hungary, the regional council of the newly formed region Burgenland took up work in Eisenstadt. A resolution was passed on 30 April 1925, which decided that Eisenstadt be the seat of the regional government and thus it became the regional capital. In 1938 Burgenland was separated into the Reichsgau Lower Danube and Styria.

Eisenstadt lost its function as regional capital.

The Expulsion of the Jewish

The expulsion of the Jewish citizens by the Nazis was a dark chapter of the town's history. A heavy bombardment on 10 May 1944 destroyed a lot of the city. 1945 red army units took over Eisenstadt. The Esterházy Palace became the seat of the regional government and Eisenstadt became the regional capital again. The Soviet occupation ended with the signing of the Staatsvertrag, a treaty signed by Austria and the allied forces in 1955. 

In 1960 Eisenstadt became the seat of the diocese Burgenland and the protestant superintendent Augsburg denomination was moved to Eisenstadt. 

In the following decades Eisenstadt was marked by a positive economic development that changed the appearance of the city.