The victory is the fifth in a row for Ellenberger, who improved to 25-5. It was also the second time in a row that Ellenberger stopped his opponent in the first round.
Beating Shields has to be extra sweet for Ellenberger. Before their fight, Shields claimed he'd never heard of Ellenberger.
The comment didn't sit well with Ellenberger.
"I can't explain how I feel right now," Ellenberger said. "Jake Shields [was] a world champion. I feel great.
"I just wanted to keep the pressure on him."
Ellenberger never gave Shields a chance to get untracked. He landed several punches early.
But it was a left knee to the stomach, followed by a right knee flush on the chin that sent Shields to the canvas. With Shields in a vulnerable position, Ellenberger began landing several punches.
Shields could no longer defend himself, and the referee jumped in to stop Ellenberger's assault.
"I'm just frustrated," said Shields, who fell to 26-6-1. "I still wanted to fight. But the ref thought it was time to stop it."
No matter the fight's outcome, it was going to be a difficult night for Shields.
The former Strikeforce middleweight champion suffered the loss of his father, Jack Shields, last month.
McGee wears down Yang
The fight was scored 30-27, 29-28 and 30-28. ESPN.com scored the bout for McGee, 29-28.
Neither fighter was aggressive during the opening round, but Yang landed the more telling strikes. But none of the strikes discouraged McGee.
He picked up his effort in the second round and forced Yang to become more defensive. Despite picking up the pace, McGee could not get Yang to the ground.
But in the third round, McGee appeared to be the fresher fighter. With blood flowing from his nose and tiring rapidly, Yang could no longer prevent McGee from taking him down.
With less than 30 seconds remaining in the bout, McGee got a takedown and landed elbows and punches.
McGee improved to 14-1. Yang fell to 10-2.
Koch stands tall in win over Brookins
He was unable to do so, and he lost a unanimous decision. The judges scored the fight 30-27, 29-28 and 30-27 for Koch. ESPN.com scored the fight for Koch, 30-27.
Brookins (12-4) was able to get Koch against the cage often in the bout, but rarely got him off his feet.
When there was distance between them, Koch hit Brookins repeatedly with right-left combinations and low kicks.
Koch, one of the fastest-rising featherweights in UFC, improved to 13-1.
Brookins had been sidelined with an eye injury. This fight against Koch was Brookins' first at 145 pounds in UFC competition.
Belcher forces MacDonald to verbally submit
Alan Belcher didn't know if he'd ever fight in UFC again after suffering a detached retina in his right eye 16 months ago.
But he returned Saturday night better than ever. Belcher punished Jason MacDonald on the ground en route to a first-round verbal submission.
MacDonald initiated the ground game by taking Belcher down. But when they hit the canvas, Belcher landed in top position.
From there Belcher began to deliver punch after punch. MacDonald had no defense for the assault and verbally tapped at the 3:48 mark.
"It feels awesome," Belcher said after winning his third fight in a row and improving to 17-6. "I've been through many trials and tribulations. I'm back.
"I'm not the fighter I used to be. When I'm on the ground, I'm just as dangerous as when I'm standing."
MacDonald is 25-15.
Rocha submits elusive McKenzie
Rocha (7-2) kept this lightweight battle on the ground and got a rear-naked choke that forced McKenzie to tap at 3:46 of Round 2.
He nearly finished the fight several times in Round 1, but McKenzie found ways to escape.
He wouldn't survive the second round. Once on the ground, Rocho applied armbars that McKenzie slipped out of. Despite McKenzie's survival skills, Rocho never stopped looking for a vulnerable position.
"I'm thrilled," Rocha said. "I worked a lot since my last fight.
"He's tough. I got him twice, but he got out of them. It's hard to get out three times."
Rocha won for the first time inside the Octagon. He lost a unanimous decision to Donald Cerrone in his Octagon debut at UFC 131 in June.
McKenzie fell to 1-2 in UFC and 12-2 overall.
Dunham beats Bailey to end skid
All three judges scored the fight 30-27 for Dunham, who used his superior striking skills to keep Bailey from executing any takedowns. ESPN.com also scored the fight for Dunham 30-27.
Fighting Bailey, who doesn't possess the skill level of Sherk or Guillard, was Dunham's best chance to get back in the win column. And he took advantage of Bailey's limited standup skills.
After punishing Bailey for the first two rounds, Dunham completely opened things up in the third. He landed right-left combinations and kicks that had Bailey covering up near the end of the bout.
But at no time would Bailey (12-4) take a backward step.
"He's a tough [fighter]," Dunham said. "I hit him with some shots that I thought would have put other guys down. He came to fight."
Stone puts Walker to sleep in first
Bantamweight Ken Stone ended a two-fight skid with an impressive first-round submission of Donny Walker.
Stone was able to get Walker to the ground, where he got his back and applied the choke. The hold was in very deep, but Walker refused to tap.
That decision resulted in Walker falling asleep and the referee jumping in to push Stone off. The end came at the 1:12 mark.
"He didn't want to tap," said Stone, who improved to 10-3. "He's a tough kid for holding on so long. I give him credit for that."
Walker was making his second appearance in the Octagon, both losses. He is 15-8 as a professional.
Baczynski returns with submission win
Seth Baczynski came out landing flying knees and hard right hands in the first round, but it was an uppercut in the second that would do the most damage to Clay Harvison.
After dominating the first round, Baczynski landed the uppercut in Round 2 that sent Harvison to the canvas. With his opponent in defensive mode, Baczynski landed numerous strikes, forcing Harvison to give his back, where Baczynski would apply a rear-naked choke.
Harvison tapped at the 1:12 mark of the second round.
Baczynski (14-6) was released by UFC after a decision loss to Brad Tavares in June 2010. He won two fights outside the Octagon before defeating Harvison.
"I want to thank [UFC president] Dana White and [matchmaker] Joe Silva and everybody for bringing me back," Baczynski said.
Waldburger chokes out Stumpf
TJ Waldburger was determined to get a submission and throughout the first round he attempted to catch fellow welterweight Mike Stumpf in a vulnerable position.
Waldburger's efforts paid off at the 3:52 mark when a beautiful transition from an armbar to a triangle forced Stumpf to tap.
The win improved Waldburger's pro record to 14-6. He is 2-1 in UFC competition. Stumpf fell to 11-3.
Fast start earns Peralta the win
Featherweight Robert Peralta defeated Mike Lullo by unanimous decision. It was the UFC debut for Peralta, who improved to 15-3.
The judges scored the fight 30-27, 30-27 and 29-28. ESPN.com scored the fight 29-28 for Peralta.
Peralta did most of his damage in the opening round, when he landed several hard kicks to Lullo's left thigh. But his most telling strike was an overhand right that left swelling near Lullo's left eye.
Lullo (8-4) came on strong in the third round, taking Peralta to the ground several times. But he could not dig himself out of the two-round hole and dropped his second fight in a row.
Early aggression gives Edwards the edge
Justin Edwards had never won a fight inside the Octagon, and he was determined to change that against Jorge Lopez.
Edwards used his superior physical strength during the first two rounds to earn a unanimous decision.
All three judges scored the bout 29-28 for Edwards, who improved to 8-1. Edwards lost a split decision in his UFC debut on June 4 to Clay Harvison.
He swayed the judges early by taking Lopez to the ground often in Rounds 1 and 2. Lopez came on strong in the third round, getting Edwards to the ground and controlling him.
But it was too little, too late. Lopez fell short in his UFC debut and his pro mark slipped to 11-2.
Franklin McNeil covers mixed martial arts and boxing for ESPN.com. Follow him on Twitter at www.twitter.com/Franklin_McNeil.