Haidian District (simplified Chinese: 海淀区 (officially), 海甸区 (alternatively); traditional Chinese: 海淀區/海甸區; pinyin: Hǎidiàn Qū) is a suburban district of the municipality of Beijing. It lies towards the northwestern part of the urban core.

It is 431 square km in area, making it the second-largest district in urban Beijing (after Chaoyang District), and is home to 2,240,124 inhabitants (2000 Census); however, in comparison to other districts, a higher percentage of its inhabitants do not have the governmental residential certificates for long-term residence, because Haidian District is where most universities are located and therefore many of its inhabitants are college students. Its postal code is 100080.