The 21-year-old Brit beat American Laura LaFrate to take home the crown and prizes including a modelling contract with LA/NY Models, a $100,000 CoverGirl contract and a fashion spread in Vogue Italia.
Sumner has also won a spread in Beauty In Vogue, the chance to be a correspondent on Extra and have a single to be released by CBS. She will also be the face of the America's Next Top Model forum Dream Come True.
After hearing that she had won, Sumner said: "Yes I did it! I never thought a Brit could win America's Next Top Model. I kept fighting and fighting, and it just shows that you will get there. I've done it.
"I'm a CoverGirl, I'm in Vogue, I am America's Next Top Model," she concluded happily.
Host Tyra Banks said: "What a journey you two have been on. [It's] interesting that you are both allies."
Banks went on to remind the two girls that only one could win and declared Sumner the victor.
"You're America's Next Top Model, so need American swagger," Banks added to Sumner.
Meanwhile, LaFrate said: "I made it this far. I got through all of this emotional stuff. I'm not just going to give up."
Earlier in the episode, LaFrate had suffered a panic attack that ultimately upset her chances to win.
Sumner and LaFrate also made America's Next Top Model history by participating in the first ever holographic runway show.
America's Next Top Model will return with a college-themed edition in the fall.