Sustainability has become the emerging goal for countries, companies, and people. Sustainability usually refers to the need to develop models necessary for both human beings and our planet to survive. However, sustainability is not a short-term problem; it is above all a long-term issue, posing intergenerational equity problems. Moreover, sustainability needs efficiency. The efficient use of energy, natural, material, and informational resources is vital for sustainability and sustainable development, which should be the major goal of every country, as established in Rio in 1992, and reaffirmed at Rio+ 20 in 2012. But any strategy aiming at sustainability and efficient use of resources must focus on innovation and technological progress. Consequently, innovation is fundamental to making sustainability possible and improving efficiency. Yet, innovation for sustainability must be environmentally friendly (e.g., green technologies). The principle behind such a strategy is better instead of more. This paper aims at highlighting the key relationship among sustainability, innovation, and efficiency. First, it examines the concept of sustainability, looking at the neoclassical literature on sustainability and its relationship with innovation. Then, it analyzes different theoretical approaches and discusses the policy issues for sustainability where innovation, natural capital, human capital, population, and institutions are fundamental factors. JEL Classification: Q32; Q38; Q50; Q55; Q56 1 The Brundtland Report (World Commission on Environment and Development 1987) follows an all-encompassing approach in which economic, social, and environmental objectives are placed on the same logical level. However, an increasingly common criticism of this approach is that it does not take sufficient account of the limits imposed by the ecosystem. In fact, in the Brundtland Report (and this is perhaps the key to its success) the natural environment does not constitute a limit for economic growth, while synergies are emphasized.