The carpel is the progenitor organ to the fruit and a defining feature of the flowering plants, or angiosperms. This organ has evolved in the angiosperms to generate a wide diversity of forms, often related to breeding strategies and seed distribution mechanisms. In this chapter, we focus on a number of key stages in the evolution of the carpel and fruit, about which something can be said of the molecular mechanisms underlying evolutionary change. In particular, we describe hypotheses for the evolutionary origin of the carpel in the first flowering plants and attempt to reconstruct the history of its structural diversification in various major angiosperm groups. In doing so, we concentrate on the genes and mechanisms whose presence can be deduced at key evolutionary stages in the angiosperms, and on molecular-evolutionary processes such as neo- and sub-functionalization, which have moulded these genes and the developmental processes they regulate. We also review the literature on the evolution of syncarpy – a phenomenon of enormous adaptive significance in the angiosperms. Lastly, we describe some examples of convergent evolution that have led to the development of fruit-like structures both within and outside the flowering plants.