Following on from Battlefield 4 being free for Prime members last month, Amazon has made Battlefield 1 free for all Prime members. You can grab it HERE and then click on the FREE GAMES tab (whilst logged in). If you don’t already have a Prime account you can get 30 days free.
This will last until August 4th, so you’ve got a bit of time to claim it and add it to your library.
Amazon has also confirmed that Battlefield V will be free from August 2nd until October 1st. you’ll be able to grab it at the same link.