Google Fonts is a library of 1029 free licensed font families, an interactive web directory for browsing the library, and APIs for conveniently using the fonts via CSS and Android. You can download all Google Fonts in a simple ZIP snapshot which is over 596MB.
Download All Google Fonts
Step 1: Download: https://codeload.github.com/google/fonts/zip/master
Step 2: Unzip To A Folder and get all Google fonts in .ttf format
These Google fonts are usually the result of collaborative projects, where you are invited to discuss issues with the designers and even contribute to their ongoing development.
When customizing or remixing fonts, please do contact the designers to understand what they might need in order to include your improvements.
Most of all: Enjoy the fonts!