地域 (dì yù) refers to a large, defined geographical region, often with shared cultural or natural features (e.g., 南方地域 'southern region'). It is more formal and broader than 区域 (qū yù), which can be any size, and less tied to administrative boundaries than 地区 (dì qū). 地方 (dì fang) is a more general 'place' or 'locality'.