At first glance, the type of effort required to solve a chess puzzle and run a marathon seem fundamentally different. This paper argues that’s wrong. I present a novel "mental-effort first" account in which all effort is fundamentally mental in nature. I outline the psychological mechanisms behind effort choice and execution, emphasizing the role of cognitive control, a mental process by which all efforts–mental and bodily–are selected and enacted. I present five arguments that convergently provide strong support for the mental-effort first account. Additionally, I examine the implications of this unified theory of effort for philosophical discussions in ethics, philosophy of mind, and action theory.