While numerous dietary regimens and pharmacological agents have been proposed to extend mammalian lifespan, none has excited the popular as well as the scientific imagination as much as rapamycin. In work conducted since 2009, numerous studies by independent laboratories have shown that rapamycin can not only extend lifespan, but can also improve health and rejuvenate aged tissues. This chapter will discuss the effects of rapamycin on aging in model organisms ranging from yeast to mice and recent efforts to assess the effects of rapamycin on age-related disease. Rapamycin inhibits the mTOR (mechanistic Target of Rapamycin) protein kinase, which has been unveiled by research over the last decade as a central regulator of metabolic processes and organismal health, and this chapter will discuss both benefits and obstacles to the use of rapamycin for the treatment of diseases of aging. Finally, we will discuss how recent developments in understanding mTOR signaling at the molecular level may lead to the development of new anti-aging pharmaceuticals with reduced side effects.