Baker Mayfield -- the hopeful future of the Cleveland Browns franchise -- just made some major life plans for the future by getting engaged to his girlfriend, Emily Wilkinson.

He made the announcement on IG, saying ... "Can't wait to do life with the most perfect girl ... I love you."

Baker and Emily were first spotted together in January -- shortly after his Rose Bowl loss -- happily taking in a Clippers game.

Then last month, Emily announced she was quitting her job in L.A. and following the Browns QB to Cleveland ... a sure sign things were getting serious.

Now it's official.