杀手级应用（Killer application），是指某个非常有用计算机进程，并且使消费者愿意为这个进程购买某个硬件软件产品的计算机进程。

• Ruby的Ruby on Rails
• Apple II的VisiCalc
• Microsoft Windows的Office

In marketing terminology, a killer application (commonly shortened to killer app) is any computer program that is so necessary or desirable that it proves the core value of some larger technology, such as computer hardware, gaming console, software, a programming language, software platform, or an operating system. In other words, consumers would buy the (usually expensive) hardware just to run that application. A killer app can substantially increase sales of the platform on which it runs.