蝰蛇科（Viperidae）又名蝮蛇科，是一个分布于全世界的毒蛇科。蝰蛇（Viperinae）和蝮蛇（Crotalinae）是这一科的代表物种，牠们体粗尾细，长着三角形的头。毒液中含有血毒素，有些种类另含神经毒素。毒牙较长，能深深刺入猎物体内高效地注入毒液。毒牙与上腭之间有关节，可在口中放倒。蝮蛇有颊窝（红外线感应器官），用以从环境温度中识别猎物的体温。大部分蝰蛇均属于夜行性动物。

蝰蛇和蝮蛇都不长，但不同各类之间体长的差异很大。纳米比亚侏膨蝰（Bitis schneideri）至多28厘米，而南美巨蝮（Lachesis muta）却可达到3.6米。

The Viperidae (vipers) are a family of venomous snakes found all over the world, except in Antarctica, Australia, New Zealand, Madagascar, Hawaii, various other isolated islands, and north of the Arctic Circle. All have relatively long, hinged fangs that permit deep penetration and injection of venom. Four subfamilies are currently recognised. They are also known as viperids.