The first urban settlement appeared in the halstatt era. The city was known in the Celtic times as Kelea when Celts used to coin money here and later on in the Roman Empire as Civitas Celeia. Setllement got its municipal rights in 46 under the name municipium Claudia Celeia during the reign of the Roman caesar Claudius. Antique Celeia had to be a wonderfull city. Written records allege it was rich and densely populated, secured with the walls and towers, full of multi-storey marble palaces, wide squares and streets. It was called the second or small Troy - Troia secunda. Celeia soon became one of the most flourishing Roman colonies.

During the great migrations of the fifth and sixth century, the city was razed. In the early Middle Ages was again renewed. The first mention of Celje in the Middle Ages was under the name of Cylie in Admont's Chronicle, which was written between the years 1122 and 1137. With the granting of the status of the Princes of the Province to the powerful Celje counts (1436), who with the support of the German Emperor Sigismund of Luxembourg (Barbara of Celje was his wife) engaged in ever more fierce clashes with the Hapsburgs for political ascendancy in Central Europe, Celje also became a princely seat for some twenty years. Even then, after the demise of the mighty Celje princes in 1456, the development of the town could not be held back. Celje acquired market-town status in the first half of the 14th century and town rights on April 11 1451 by orders from the Celje count Frederic II (Friderik II).

By the 18th century Celje was already famous as a flourishing craft, manufacturing and mercantile centre.

With 1st World War underway, each person needed to take sides. All the way to the fall of the Austrian monarchy in 1918, two mottos were present in the political and social scene: in German "Hie Deusche - hie Slowenen"; in Slovene "Svoji k svojim" ("Every man to his own"). Because of Celje and Celje citizens and Slovene parallel classes at Celje gymnasium 1895 even fell Austrian government of Alfred Windischgraetz. That was those days a real precedent.

The balance of a 2nd World War was terrible. The city had 20,000 citizens (with nearby towns) and lost 575 people, mostly young ones between 20 and 30 years old. More than 1500 people were ejected to Serbia or into the interior of the German Third reich. Around 300 people were interned and around 1000 people prisoned in Celje prisons. An unknown number of the citizens of Celje were forcibly mobilized in the German army. Many were children. Around 600 "stolen children" were taken to Germany for Germanization. A monument in Celje entitled "Vojna in mir" ("The war and the peace") exists to commemorate these times.

After World War II, Celje expanded its industry, mainly chemicals and metalworking but also the timber, printing, and textile industries, and banking. Commercial and marketing activities increased as well. A thriving food-processing industry developed, especially milling, baking, and meat-processing with their centuries-old tradition. The proclamation of the independent Republic of Slovenia in 1991 represented yet another turning-point for the town and Municipality of Celje. In recent years, new forms of trade and business have flourished and are now replacing the more traditional heavy industry. Within the business structure the latter have been replaced by numerous smaller companies that are engaged in promotion of economic progress and growth. Among the more than fifteen fairs organized annually, the International Trade Fairis the second largest of its kind in Europe. This has made Celje into an important international commercial center.

From: http://www.fact-index.com/c/ce/celje.html