This paper investigates the concept of effective human oversight in the context of high-risk AI applications. It synthesizes insights from psychology, law, philosophy, and technical domains to propose a viable understanding of effectiveness in human oversight. The main objective of human oversight is risk mitigation, and for an oversight person to be effective, they must have sufficient causal power with regard to the system and its effects, suitable epistemic access to relevant aspects of the situation, self-control, and fitting intentions. The paper argues that this is equivalent to saying that an oversight person is effective if and only if they are morally responsible and have fitting intentions. The paper also discusses factors in three domains: the technical design of the system, individual factors of oversight persons, and the environmental circumstances in which they operate. It examines the European AI Act as an example of a regulatory framework in which the practicality of the proposed understanding of effective human oversight is studied. The paper identifies possible benefits and shortcomings of the AI Act and argues that the proposed conceptualization provides both a more general and more practically useful conceptualization of effective human oversight compared to the respective stipulations in the AI Act. The paper also discusses the importance of moral responsibility and fitting intentions in effective human oversight. It highlights the need for clarity on the concept of effective human oversight to better devise powerful laws and guidelines and to ensure the successful and safe implementation of AI in high-risk contexts. The paper concludes that effective human oversight is a complex and multifaceted concept that requires adaptability and versatility to address the diversity of situations in which it is applied.This paper investigates the concept of effective human oversight in the context of high-risk AI applications. It synthesizes insights from psychology, law, philosophy, and technical domains to propose a viable understanding of effectiveness in human oversight. The main objective of human oversight is risk mitigation, and for an oversight person to be effective, they must have sufficient causal power with regard to the system and its effects, suitable epistemic access to relevant aspects of the situation, self-control, and fitting intentions. The paper argues that this is equivalent to saying that an oversight person is effective if and only if they are morally responsible and have fitting intentions. The paper also discusses factors in three domains: the technical design of the system, individual factors of oversight persons, and the environmental circumstances in which they operate. It examines the European AI Act as an example of a regulatory framework in which the practicality of the proposed understanding of effective human oversight is studied. The paper identifies possible benefits and shortcomings of the AI Act and argues that the proposed conceptualization provides both a more general and more practically useful conceptualization of effective human oversight compared to the respective stipulations in the AI Act. The paper also discusses the importance of moral responsibility and fitting intentions in effective human oversight. It highlights the need for clarity on the concept of effective human oversight to better devise powerful laws and guidelines and to ensure the successful and safe implementation of AI in high-risk contexts. The paper concludes that effective human oversight is a complex and multifaceted concept that requires adaptability and versatility to address the diversity of situations in which it is applied.