藤原效应（英语：Fujiwara effect），是指两个距离不远的水旋涡或大气旋涡（例如热带气旋），因为涡度、质量及相对位置的不同，而互相影响的状态。藤原效应最早是由当时的日本中央气象台（今日本气象厅）台长、日本气象学家藤原咲平在1921至31年间所进行的一系列水工实验及研究发表，主要解释当两个台风同时形成并互相靠近时所产生的交互作用，因而得名。藤原咲平发现，两个接近的水旋涡，它们的运动轨迹会以两者连接的中心为圆心，绕着圆心互相旋转。而大气旋涡亦出现类似情况。

The Fujiwhara effect, sometimes referred to as Fujiwara interaction or binary interaction, is when two nearby cyclonic vortices orbit each other and close the distance between the circulations of their corresponding low-pressure areas. The effect is named after Sakuhei Fujiwhara, the Japanese meteorologist who initially described the effect. Binary interaction of smaller circulations can cause the development of a larger cyclone, or cause two cyclones to merge into one. Extratropical cyclones typically engage in binary interaction when within 2,000 kilometres (1,200 mi) of one another, while tropical cyclones typically interact within 1,400 kilometres (870 mi) of each other.