Nunes is still three successful title defenses short of Ronda Rousey's UFC women's record of six, but it's worth noting that Rousey defended the Strikeforce Women's Bantamweight title once more before being awarded the UFC title.
A fired-up Nunes started the contest light on her feet and full of confidence, which she exuded throughout fight week.
From the third round on it seemed smooth sailing for Nunes who wasn't affected by Pennington's strikes, walking forward and landing her own attacks whenever she pleased.
Between rounds, Pennington's corner urged her not to allow Nunes to march her down and keep her back against the fence.
Nunes tripped Pennington up with a leg kick early in the first round and was the aggressor throughout the fight.
After a pair of failed attempts while backed against the cage, Pennington scored a takedown of Nunes late in the second round to slow the steady onslaught from the champion. "This is the first time", Nunes said.
Before the decisive round, Pennington was heard saying "I'm done", but her coach insisted she should return to the bout. At the end of the fourth, she laid into Pennington with knees from the clinch.
Pennington got her chance on May 12, but did not come home with the gold.
Pennington finally rolled over with Nunes just pouring on the punishment as the canvas was painted red with blood until the referee saw enough to step into stop the carnage. This earned the Brazilian a stoppage at the 2:36 mark of the final round. Gastelum poured on the strikes in the second round and got a knockdown on a stiff left hand.
And even after taking down the former Team Tate star, Nunes was met with more doggedness from Pennington, who was fast running out of ideas of how to dethrone the Brazilian.
'Michael Bisping, I'm still waiting for you, man, ' Machida said in his post fight interview.