The town of Krnov is situated at the junction of rivers Opava and Opavice in the piedmont of Low Jeseník alongside the Czech-Polish border. Archaeological finds reveal that this place has been almost continuously settled since the Old Stone Age, approximately 30 000 years.

As late as the 7th century the settlement was exclusively Slavic as it is also evidenced by written reports about the Moravian tribe of Holasics. Erratic blocks and other material brought to Krnov by the glacier are permanent reminders of the glacial epoch. From the post- glacial epoch there were found in Krnov a cave bear´s canine tooth, a fragment of mammoth´s molar and other finds. Life of  Young Stone Age is documented by extensive finds in nearby Brumovice; fortified settlements on both Cvilín hills date back to the last period of Neolite.

In the period of the culture of urn fields people  there were three fortifications:
on the front Cvilín hill, above Červený dvůr on the adjacent part of the Úvalno cadastre and on the rear hill. From here also come finds from the near surroundings, primarily iron pots and an iron axe from the 11 and 12th century.

The date of origin of Krnov itself cannot be unquestionably determined. Its Czech name (in the form of Kyrnow) is documented in the first written form in 1240. The German name Jägerndorf (in the form of Jegerdorf) is first recorded in 1253. In medieval documents the place was also referred to by a Latin name Carnovia. Krnov originated at the crossroads of ancient merchant routes connecting Baltic Hanseatic towns with Italy.

It first appears in historic documents from year 1240 in the Act of Czech King Václav I in which he donates to the Tišnov monastery a hide row village popularly called Kyrnow in the former Holasics region ("circulium quendam in districtu Holascencsi, Kyrnow vulgariter nuncupatum cum omnibus appendiciis suis, villis,  agris,  pratis, silvis, fluminibus")

It soon receives municipal prerogatives. This happened before year 1269. It can be said that during the rule of Přemysl Otakar II Krnov had these prerogatives. Municipal privileges were confirmed by Queen Kunhuta in year 1279. The Krnov castle Cvilín built from stone in the 13th century became a princely residence of the Opava prince Mikuláš from the indirect Přemysl line when at his arrival in the Opava region he was received by independent administrative institutions - municipal court and Krnov municipal law, Moravian Margrave Jošt introduced municipal tablets and office of municipal governor. The Krnov region has become a significant territorial unit lying on the dividing line between Moravia and Silesia.