She took out Sara McMann with a vicious knee to the body. Now the champion will go off to film a couple of movies before returning to defend her title once more.
There were 10 more fights on the card and a lot of talking points after the event. Many top contenders made statements on both the main and preliminary cards. Raphael Assuncao made his case for being next in line for Renan Barao's bantamweight strap, and Alexis Davis may be next up for Rousey.
Following the event, some fighters improved their position, while others took a step back.
Here is a look at the UFC 170 post-fight stock report.
Erik Koch took care of business against Rafaello Oliveira.
Koch went back up to 155 pounds after an extended period of trying to become a title challenger at 145. As a young fighter, his body started to mature, and the move to lightweight just made sense. He looked reinvigorated at 155, and it showed in his performance.
Oliveira isn't a Top 15-caliber fighter, but he is a serviceable lightweight. Koch passed the test.
It will be interesting to see where the UFC puts him next. Does he face a potential Top 15 fighter, or will the UFC take the time to rebuild the youngster? It may be telling for his development and future prospects in the division.
Nevertheless, he put himself on the right track at UFC 170.
Six undercard bouts, five decisions. Welcome to the UFC in 2014.
Fights do not have to be finished to be exciting, but UFC undercard bouts in 2014 have not been stellar. UFC 170 continued with decisions, but it did have more exciting bouts than other cards this year. So, a small positive can be taken away.
Despite the somewhat exciting bouts of Alexis Davis vs. Jessica Eye and Aljamain Sterling vs. Cody Gibson, the preliminary bouts failed to deliver on the scale that they have in years past.
Did these bouts make you want to order UFC 170? Did they pump you up at all? Not likely.
The UFC needs to find an answer to its preliminary card problem.
"Wonderboy" burst onto the UFC scene with a swift knockout at UFC 143 and then suffered a setback against Matt Brown.
Since that loss, he posted back-to-back wins. He extended that to three straight at UFC 170 with a stellar TKO finish of Robert Whittaker.
Stephen Thompson has silently begun to climb the welterweight ranks. He brings in a unique skill set that confounds his opposition. He made a statement in the main card's opening bout, which should move him into a position for a significant fight in his next outing.
Wonderboy has emerged as a legitimate prospect at 170 pounds.
Herb Dean is one of the best referees in the business, but his stock has dropped recently. UFC 170 continued that trend.
In the Mike Pyle vs. TJ Waldburger fight, he was late on the stoppage. Waldburger took a ridiculous amount of unnecessary punishment. Pyle bludgeoned the youngster, and Dean watched it happened. It was not a good look.
Later in the night, Dean was the man in the cage with Ronda Rousey and Sara McMann. While the stoppage was justified, Dean could have let it go a bit longer. McMann was not in nearly the same amount of trouble that Waldburger was in, and it was a title fight.
Did his earlier stoppage play a role in the main event, was it just an off night or is he regressing?
My guess is that it was just a bad night, but it is worth keeping an eye on.
Rory MacDonald and Demian Maia entered UFC 170 looking for a win to put them back in title contention. The victor was MacDonald.
Maia put MacDonald on his back in the first, and "Ares" survived against one of the top grapplers in the world. More impressively, he came back stronger in the final two rounds.
MacDonald was methodical but exciting in the process. He turned up the pressure when he felt Maia wilt, put together good combinations on the feet and showed why he is one of the best welterweights going today.
He put himself right back in the mix at 170 pounds.
Demian Maia could have maintained his spot in the UFC welterweight division by being competitive throughout, but he showed why he is not a title contender.
He does not have the gas tank to compete with the elite.
He puts everything into his fights early on. He shoots from way outside, wings big power shots and has a good pace. But it all takes a big toll on his conditioning. He was noticeably slower in the second round, and nothing he threw at MacDonald was crisp.
Maia is essentially a gatekeeper now.
If fighters can get past him, they are contenders. That is his role. While it is needed in the stacked welterweight division, it is not the role that Maia wanted to find himself in.
Daniel Cormier was expected to walk right through Patrick Cummins. So, why did his stock increase?
Because he did exactly that.
He has been criticized in the past for being overly technical against overmatched competition. At UFC 170, Cormier destroyed Cummins. He looked like an elite fighter taking out an amateur.
The undefeated wrestler came off looking like the title challenger that he is. That is big for him moving forward. He won't likely get the next title shot, but he is in the position that he wants to be in at 205.
How can Ronda Rousey's stock climb any higher? By adding in more elements to her game, showing them off and taking out elite competition.
Sara McMann was supposed to be Rousey's first real challenge. Someone who could take her down and keep her down.
Instead, Rousey gave her a knee to the liver and ended the fight in less than 90 seconds. She finally showed off her striking in a fight, and it ended it quickly as a result.
More importantly, she showed amazing fight IQ. She knew how McMann would react, placed the knee with pinpoint accuracy and won the fight.
High fight IQ is hard to come by. Not every elite fighter has it. Many simply get by on talent, but when talent meets a mind like Rousey's, you get fantastic results. She analyzes her opponents and knows exactly how to take them out with minimal effort.
Rousey is the greatest female fighter of all time.