National Library Station (Chinese: 国家图书馆站; pinyin: Guójiā Túshūguǎn Zhàn) is an interchange station on Line 4 and Line 9 of the Beijing Subway in China. The station features a double-island interchange layout, with Line 4 trains on the outside and Line 9 trains on the inside, which allows most riders to change lines simply by crossing the platform, instead of walking between levels. This configuration is known as cross-platform interchange. The station handles 106,000 transfers between Lines 4 and 9 per day.