The discussion focuses on the period and circumstances surrounding the relatively late emergence of the medieval market town of Šoštanj. Its establishment may be dated to sometime after 1330, when the lords of Sannegg (Žovnek) inherited a sizeable estate from the Counts of Heunburg (Vovbre), who became extinct in 1322. Given that during the Heunburg period, the documents for the Šoštanj area only confirm the existence of a seigniory with the village of Družmirje as the central settlement within its boundaries, the founding of the market town may be attributed to the free lords of Sannegg, later Counts of Cilli (Celje). Since its establishment, Šoštanj was the economic centre of the Žovnek area between the Lower Savinja Valley and the Upper Savinja or Šalek Valley and as such a direct rival to the older market town of Velenje, already founded in the mid-thirteenth century and owned by the lords of Königsberg (Kunšperk) or, rather, their relatives, the lords of Pettau (Ptuj). It was also with the support of the Sanneggs that Šoštanj quickly outgrew Velenje and asserted itself as the major economic centre in the Šalek Valley, although, as Šoštanj’s oldest market town privileges reveal, the rivalry between the two nonetheless continued well into the Early Modern Period. While the documents testify to Šoštanj’s struggle to secure its monopoly on weekly fairs and salt trade with Slovenj Gradec, which Velenje sought to chip away at, they do not enable a serious reconstruction of the market town’s (self-)administration. Although Šoštanj already had its own judge in the fourteenth century, the latter appears more to have represented the market town’s lord than the market town and its self-administration. On the other hand, in view of the complete absence of data regarding the market-town council, not only nothing is known about the number of its members and how they were selected, but there is also no knowledge about whether or not it even existed. The first documents indisputably attesting to its existence emerged in the sixteenth century. Despite the modest data available, the list of lesser nobility that worked in Šoštanj and its surroundings demonstrates that the market town was also very attractive for noble settlers and that it was an economic (as well as probably judicial and administrative) centre of major significance. This may perhaps be the best way to explain the presence of a considerable number of noble families. A new period in the history of Šoštanj began in 1456, following the extinction of the male line of the market town’s lords, Counts of Cilli, who were succeeded by the Styrian provincial lords of Habsburg after a brief period of the so-called struggle for the Celje heritage. Reduced to a less important part of the Habsburg estates, Šoštanj entered its new, early modern era. The relatively rapid development of the settlement in the fourteenth and the first half of the fifteenth century was followed by a calmer stage in its history, which lasted until the end of the eighteenth century, when the market town began to prosper again with the emergence of its leather industry.