Yes, you can download Wikipedia...all of Wikipedia

The website that put the encyclopedia to death is yours for the downloading. Wikipedia is the world’s most popular and up to date encyclopedia. It is like an external brain of sorts that we can access anytime to gain knowledge about hundreds of thousands of topics, but only as long as we have internet access. That really doesn’t have to be the case though, since you can use Kiwix to download and read the entirety of Wikipedia completely offline. The program is available as a portable application, but can also be installed the traditional way. When you launch it for the first time, it asks you to download the catalogue of available wikis, which you definitely must download. I didn’t understand it at first, so I pressed no; ‘Do not ask anymore’ was enabled by default so I had to reinstall the program to be able to one-click download the catalog.
It's a great tool that will give you Wikipedia, even without an internet connection. Give it a try!