Default Router Username and Password lists.
To login to your router's web interface you'll need the admin username and password. If your router is new or hasn't otherwise been modified, you can access it with the router defaults.
Most routers from the same manufacturer will use similar, if not exactly the same passwords. But there are also cases when the models vary quite a bit.
Check the table below for the most common usernames and passwords for various router brands.
Since many models from the same brand can vary a bit with blank username/password you might need to go to the specific brand page to find your model.
If all else fails and you can't use the default username and password, you can always check the router reset instructions to get the router to it's default.