Bethesda has revealed what sort of system it will take to run Fallout 4, and it's looking good: so long as you have a mid-range graphics card from 2010 or newer paired with 8 GB of RAM, you'll be able to run one of the most hotly anticipated games of 2015.
|CPU||Intel Core i7 4790 3.6 GHz
AMD FX-9590 4.7 GHz
|Intel Core i5-2300 2.8 GHz
AMD Phenom II X4 945 3.0 GHz
|GPU||NVIDIA GTX 780 3GB
AMD Radeon R9 290X 4GB
|NVIDIA GTX 550 Ti 2GB
AMD Radeon HD 7870 2GB
|OS||Windows 7 64-bit or newer|
Fallout 4 will be released on November 10th, and it will require a 64-bit version of Windows like many current-generation games. You'll also need to free up 30 GB of space to install the game, though that shouldn't come as a huge surprise considering its open-world nature.
As for recommended requirements, Bethesda suggests either a Nvidia GeForce GTX 780 or AMD Radeon R9 290X to get the best Fallout 4 experience. The game is shaping up to have fairly decent graphics, but it doesn't look like a hugely demanding game to run.
Interestingly, Bethesda lists the GeForce GTX 550 Ti as the minimum Nvidia graphics card that's required, but on the AMD front, the significantly more powerful Radeon HD 7870 is required. Does this mean the game will run significantly better on Nvidia hardware? Probably not, but it's an interesting discrepancy to note.