广告软件是一个附带广告的电脑进程，以广告作为盈利来源。

部分广告软件以广告为目的，例如会不断弹出「电脑网络」或「系统性能低落」等广告。许多用户未经详查，便会不慎地经由同意免费软件的最终用户许可协议（EULA），而安装了以广告为目的的广告软件。也可以由其他人安装在别人的电脑上，有时甚至并未经其许可。有的会自动运行，虽然大部分对电脑无害，但通常这类程序经常在系统中造成恼人效果，并多少会影响用户使用电脑。这类软件通常经由与特定免费软件搭配分别安装。广告软件也经常与间谍软件串连起来安装。

除了以广告为目的的广告软件之外，还存在免费软件通过绑定界面广告或者少数弹出广告达到其盈利目的，例如腾讯QQ、迅雷等。

Adware, or advertising-supported software, is any software package that automatically renders advertisements in order to generate revenue for its author. The advertisements may be in the user interface of the software or on a screen presented to the user during the installation process. The functions may be designed to analyze which Internet sites the user visits and to present advertising pertinent to the types of goods or services featured there. The term is sometimes used to refer to software that displays unwanted advertisements known as malware.