奥司他韦（INN：Oseltamivir）是一种作用于神经氨酸酶的特异性抑制剂，其抑制神经氨酸酶的作用，可以抑制成熟的流感病毒脱离宿主细胞，从而抑制流感病毒在人体内的传播以起到治疗流行性感冒的作用。奥司他韦是基于结构的合理药物设计的成功案例，在这种药物的研发过程中大量应用了计算机辅助药物设计的手段，根据靶酶的三维结构有针对性地设计了高效低毒专一性强的神经氨酸酶抑制剂。

罗氏制药有限公司是奥司他韦的专利持有人，目前他们生产的奥司他韦磷酸盐胶囊剂（商品名Tamiflu，中国大陆称达菲，港译特敏福，**译为克流感）是市场上唯一的奥司他韦制剂。2005年10月间，由于禽流感在世界范围的扩散，全球掀起一股抢购的风潮，罗氏也因为不肯开放奥司他韦的专利权、限制销售等行为而遭到广泛的谴责。2009年的H1N1新流感及2013年H7N9流感亦使用奥司他韦作治疗。

Oseltamivir, marketed under the trade name Tamiflu, is an antiviral medication used to treat influenza A and influenza B (flu), and to prevent flu after exposure. The medication is taken orally.

The Infectious Disease Society of America, the United States' Centers for Disease Control and Prevention (CDC), and the United Kingdom's National Institute for Health and Care Excellence recommend the use of oseltamavir for people who have complications or are at high risk for complications who present within 48 hours of first symptoms of infection. They recommend its use to prevent infection in at-risk people but not the general population. The CDC recommends that clinicians use their discretion to treat those at lower risk who present within 48 hours of first symptoms of infection. However, these recommendations are controversial as are criticisms of the recommendations. A Cochrane review concluded that oseltamivir does not reduce hospitalizations, and that there is no evidence of reduction in complications of influenza (such as pneumonia) because of a lack of diagnostic definitions, or reduction of the spread of the virus. Two meta-analyses have concluded that benefits in those who are otherwise healthy do not outweigh its risks. They also found little evidence regarding whether treatment changes the risk of hospitalization or death in high risk populations. However, another meta-analysis found that oseltamivir was effective for prevention of influenza at the individual and household levels.