Raspbian is a GNU/Linux operating system specially designed and optimised for Raspberry Pi.
You can download latest Raspbian version on this page.

Raspbian Jessie

The latest version of the full Raspbian OS, rather adapted to Raspberry Pi 2 and Raspberry Pi 3
SHA-1: e1edd4d26090b3e67a66939fa77eeb656de8a2c5

Raspbian Jessie Lite

You can download a smaller version of Raspbian, rather adapted to Raspberry Pi A+ or Raspberry Pi Zero
SHA-1 : 30a171e10eb0b93b0e552837929c504d1bacd755
Download in progress...
While downloading your file, you could do a coffe and drink it by reading our article on the choice of Raspberry Pi accessories