Polygyny is the sociological practice of one man having more than one female partner. It is the most common form of the practice of polygamy. (Polyandry being the reverse, one female with many male partners.) Polygyny comes, naturally enough, from the Greek poly- ("many") and gyno- ("woman").
In the lower animal species, polygyny is far from rare, although the term is usually reserved for practicing a form of controlled polygny. Whereas for most species, males tend to have multiple partners due to the limitations of pregnancy, it is uncommon to find species where females are bound to one male while males are free to copulate among the many females.
Although polygyny has been seen throughout practically all of human history, it is generally frowned upon in modern societies as degrading to women and socially inhibiting.
Famous incarnations of polygyny include the fabled harems and concubines of the Middle East, the early practitioners of the Mormon church, the ancient Chinese and Indian peoples, and of course, the Hebrews of the Old Testament, where polygyny and its effects play a role in a number of famous Biblical stories.