iOS (iPhone/iPad/iPod Touch)
If you have a different model iPhone, iPad, or iPod Touch
There are some mobile browsers that have ad-blocking built in, such as Opera and the browser developed by our friendly rival, Adblock Plus (ABP).
If you want to block ads in apps, not just on web pages
We also found some content blockers that block ads in apps (not just in a web browser), by blocking ads at the network level using a VPN (Virtual Private Network). Opera Free VPN is popular, highly rated, and free. For others, look for "vpn ad blocker iphone" in your favorite search engine.
Android
If you use Firefox
You can get AdBlock for Firefox Mobile in the Firefox Addons store in your browser.
If you want to block ads in apps, not just on web pages
There are also ad blockers that block ads in apps, by blocking ads at the network level using a VPN. Some of them require root access to your device, but some don't. Opera Free VPN and Adblock Plus for Android are highly rated and free and can be used on an unrooted device. For others, look for "vpn ad blocker android" in your favorite search engine.
Windows Phone
Try Opera or the Adblock Plus browser, both of which have ad-blocking built in. As far as we know at this time, there are no ad blockers that work in other Windows Phone apps.