锡尔河（英语: Syr Darya，哈萨克语：Сырдария，乌兹别克斯坦语：Sirdaryo，波斯语：سیردریا‎，塔吉克斯坦语：Сирдарё），中国古称药杀水，也即叶河，中、下游流经沙漠地区，是中亚著名内流河。

锡尔河发源于天山山脉，分两源，右源纳伦河和左源卡拉达里亚河，纳伦河为正源，发源于吉尔吉斯斯坦。两河在纳曼干附近汇合后向西流入费尔干纳谷地，在塔吉克斯坦斯坦苦盏出谷，流至别卡巴德后转而向西北，流经乌兹别克斯坦和哈萨克斯坦后，注入咸海。

全长2212公里，流域面积21.9万平方公里，河口多年平均流量1060立方米/秒，年均径流量336亿立方米。

The Syr Darya /ˌsɪərˈdɑːrjə/ (Kazakh:Сырдария; Russian:Сырдарья́, tr.Syrdar'ya;IPA: [sɨrdɐˈrʲja]; Persian:سيردريا‎‎; Tajik:Сирдарё; Turkish:Seyhun, Siri Derya; Arabic:سيحون‎: Seyhun; Uzbek:Sirdaryo) is a river in Central Asia.

The Syr Darya originates in the Tian Shan Mountains in Kyrgyzstan and eastern Uzbekistan and flows for 2,212 kilometres (1,374 mi) west and north-west through Uzbekistan and southern Kazakhstan to the remains of the Aral Sea. It is the northern and eastern of the two main rivers in the endorrheic basin of the Aral Sea, the other being the Amu Darya. In the Soviet era, extensive irrigation projects were constructed around both rivers, diverting their water into farmland and causing, during the post soviet era, the virtual disappearance of the Aral Sea, once the world's fourth-largest lake.