Whole crop rice silage (WCRS) is a type of cattle feed made by harvesting both rice grains and straws together and then ensiling them. In Japan and South Korea, significant efforts have been made in the production and utilization of WCRS to address the increasing crop rotation and idle rice fields, rising imported feed prices, and the need for safe livestock products. Since 2000, advancement in WCRS has included the development of specialized rice varieties, harvesting machinery, and silage feed additives, which have greatly improved its fermentation quality and nutritional value. As a result, the area planted with WCRS has rapidly expanded. This chapter focuses on the varieties of WCRS, the machinery used, and the additives specifically used in Japan and South Korea. It covers aspects of harvesting and preparation, feed characteristics, and the effects of WCRS on cattle feeding.