The system of rice intensification (SRI) is a combination of management practices developed in Madagascar some 30 years ago to make the cultivation of irrigated rice more productive. This chapter reviews how the SRI has evolved over the past 15 years as its efficacy has been demonstrated in over 50 countries. It reviews the ways in which SRI thinking and practice have developed as a result of farmer experience and scientific research, offering higher factor productivity, increased food security and poverty reduction, with more sustainability and climate-resilience in rice production. This review shows how SRI ideas and practices continue to evolve and even have effects beyond irrigated rice production to improve productivity for rain-fed rice and other crops.