Relative to presidentialism and parliamentarism, the study of semi-presidentialism is still in its infancy. The term was coined in 1970 and, apart from the pioneering work of Maurice Duverger, systematic study began only in the 1990s. Previously, the definition of semi-presidentialism was the subject of much debate. Now, most scholars agree that semi-presidentialism is where there is both a directly elected fixed-term president and a prime minister and cabinet that are collectively responsible to the legislature. The key contribution of recent scholarship is that semi-presidentialism is not a unimodal category. Instead, there is a tremendous variety of executive politics in countries with a semi-presidential constitution. This work has identified the effects of such variation on topics such as democratic performance and both government formation and termination. Given so many countries now have semi-presidential constitutions, the study of this topic is likely to remain salient. In the future, there should be more comparative studies of semi-presidential countries and more systematic comparisons of semi-presidentialism with presidentialism and parliamentarism.