This e-book has been edited from the printed version. The edition is divided into twelve chapters, and covers from the origin, evolution and domestication of alfalfa, to traditional methods and biotechnological techniques applied to improving this forage plant. It is a collection that gathers information of interest to researchers, teachers and students of Agronomy and Zootechny, constituting a useful work to the national scientific community. The edition brings together current knowledge available in various institutions (Embrapa Agrobiology, Embrapa Dairy Cattle, Embrapa South Livestock, National Institute of Agricultural Technology of Argentina, State University of Maringá, Federal University of Lavras, Federal University of Viçosa) with the contribution of 17 authors, who are agronomists, geneticists and biologists. One of the barriers to expanding the alfalfa crop in Brazil is the lack of cultivars adapted to tropical conditions, despite the great demand for new-release ones on the market. The development of new alfalfa cultivars will enable it to be cultivated in different regions of Brazil, resulting in an increase in its area of exploitation, and will thus ensure high quality and high productivity feed for intensive milk production systems.