Harm, intention, and responsibility are the central concepts around which contemporary discussions on ethics, political philosophy and philosophy of action take place. Our research fits into recent philosophical discussions that analyze the meaning of these concepts as well as their normative implications in the various domains of our everyday life. In this research, we start from the assumption that the concept of harm is a constitutive part of moral practice: if an action causes harm, then such action – in the absence of other relevant considerations – is morally impermissible. However, in trying to give a better understanding of this notion, philosophers have realized that things are not so simple and that the notion of harm opens up many questions that are still to be answered. What is harm and what does it mean to harm someone? Is there a morally relevant difference between doing harm and allowing harm? Is there a morally relevant difference between harm that is intentionally brought about and harm that is brought about as a side effect of some action? Are we responsible only for harm that we have intentionally caused or is the practice of attributing responsibility immune to the question of how harm came about? In the attempt to answer these questions, we will critically consider the existing theories of harm and try to evaluate them in view of their ability to explain different phenomena (for example, the phenomenon of death and the phenomenon of harming future people). We will also examine the assumption according to which the moral status of an action may ultimately depend on the reasons for which the action is performed. In that sense, we will determine if the difference between intentionally and unintentionally causing harm can be of relevance to the question of what is morally permissible. A significant part of the research will focus on who can bear responsibility for harm. Are only individuals responsible for harm or is it sometimes possible to speak about collective responsibility? In view of the above, our research will be divided into three parts: (1) The nature of harm; (2) Harm and the moral significance of intentions; and (3) Individual and collective responsibility. In the last phase of the research, we will combine previously achieved results with the aim of obtaining a unique and coherent image of how these notions are related to each other.