The purpose of the research is the analysis of the concept of bad faith in the sphere of trade marks from the perspective of a fair balance of different interests of the trade mark proprietor and other undertakings in the European market. On the one hand, the starting point of European trade mark law is the protection of exclusive rights conferred on the owner of a registered mark. On the other hand, Article 16 of the Charter of Fundamental Rights of the European Union guarantees the right to free access to the market. The research work analyses the scope of these conflicting rights and comes to the conclusion that the interests of trade mark law and market competition may have common ground despite different starting points between them. Bad faith behaviour in the market should also be assessed as an acute common issue. In that connection, the objective of the thesis is to examine how the balance of the interests is achieved in European trade mark legislation and in practice, whether this balance is fair when dealing with bad faith. Additionally, the thesis considers the issues of the definition of bad faith in European legislation and possible changes in the European trade mark system related to the concept of bad faith.