路易士·阿格西（Jean Louis Rodolphe Agassiz，1807年5月28日－1873年12月14日），19世纪瑞士裔植物学家、动物学家和地质学家，以冰川理论闻名。

阿格西生于瑞士西部，分别在德国Erlangen和慕尼黑获得哲学博士和医学博士学位。在前往巴黎与居维叶和冯·洪堡学习之后，阿格西成为纳沙泰尔大学的自然史教授。

1847年，阿格西移民美国，在哈佛大学任教，担任动物学和地质学教授。在这里，他领导劳伦斯科学学校，创建了比较动物学博物馆。阿格西对鱼类学分类法和地质学贡献卓着，是冰川学的开创者。

Jean Louis Rodolphe Agassiz (English /ˈæɡəsi/; French: [agasi]; May 28, 1807 – December 14, 1873) was a Swiss-American biologist and geologist recognized as an innovative and prodigious scholar of Earth's natural history, with later American writings that have received scrutiny because of particular racial themes. Agassiz grew up in Switzerland, and studied and received Doctor of Philosophy and medical degrees at Erlangen and Munich, respectively. After further studies with Cuvier and von Humboldt in Paris, Agassiz proceeded with research leading to his appointment as professor of natural history at University of Neuchâtel.