In the area of corporate investment policy and governance, one of the most widely-studied topics is corporate “short-termism” or “investment myopia”, which is the practice of preferring lower-valued short-term projects over higher-valued long-term projects. It is widely asserted that short-termism is responsible for numerous ills, including excessive risk-taking and underinvestment in R&D, and that it may even represent a danger to capitalism itself. Yet, short-termism continues to be widely practiced, exhibits little correlation with firm performance, and does not appear to be used only by incompetent or unsophisticated managers (e.g. Graham and Harvey (2001)). In A Theory of Efficient Short-termism, I challenge the notion that short-termism is inherently a misguided practice that is pursued only by self-serving managers or is the outcome of a desire to cater to short-horizon investors, and theoretically ask whether there are circumstances in which it is economically efficient.