祖孝孫（562年 - 631年），字德懋，隋唐時期樂律學家。

曾祖祖瑗，魏東魯二郡、鍾離侯。祖祖遵，魏衛將軍、右光祿大夫、淮川公。父祖崇儒，官至齊州長史。祖孝孫精曆算數學。隋初開皇年間任協律郎，參定雅樂、京房律法。曾向陳山陽太守毛爽學習「京房律法」。唐初任太常少卿，教宮女音樂。教得不好，宮女沒有長進，太宗責怪孝孫。王珪與溫彥博替祖孝孫辯解：「孝孫雅士，今乃令教宮人，更加譴責，毋乃非宜。」太宗更加生氣，王珪據理力爭。《新唐書》有傳。

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Zu Xiaosun was a Chinese musician of the Sui and Tang dynasties. During the Kaihuang reign period (581–600) of Emperor Wen of Sui he was appointed as Xielülang (协律郎), joined the melodizing of ritual music, and received orders to learn the Jing Fang Temperament (京房律法) from Mao Shuang (毛爽). After the founding of Tang Dynasty, Zu served as zhuzuolang (著作郎), libulang (吏部郎) and taichang shaoqing (太常少卿).

From 626 to 628, Zu composed music for Emperor Gaozu of Tang. Zu cooperated with (张文收), solved the problem of tuning (调律) and change of keys of twelve temperament (十二律旋宫).

All Zu's works about music temperament had already been lost, only some summaries of his theory were recorded by Annals of Music (音乐志) and Annals of Rites and Nusic (礼乐志).