Bruno's Onix (Japanese: シバのイワークSiba's Iwark) is a Pokémon caught by Bruno in To Master the Onixpected!. It is another giant Pokémon that appeared in the anime, and one of Bruno's Pokémon in the games.
This giant Onix was first seen rampaging wildly around the Mt. Hideaway. Ash and friends tried to stop it with their Pokémon, but didn't succeed. Bruno then appeared, ready to catch Onix. When Ash and the others asked what Pokémon he was going to use, Bruno shocked them by telling that he wasn't going to use any Pokémon. After a while, Bruno found the reason why Onix was on a rampage: a Sandslash had been stuck inside it and was hurting it. After Bruno removed the Sandslash, Onix became very thankful for him and accepted to join his team, so Bruno threw a Poké Ball at Onix and captured it. It hasn't been seen since.
Bruno used his Onix to battle Red during their battle on Mt. Moon. Despite a type disadvantage against Red's Gyarados, it was able to hold its own and deftly avoid super-effective hits from its Water-type attacks. Afterwards, it used its Bind to keep the Gyarados from attacking at all, only to take damage from the latter's Bite. It then dug underground to launch a surprise attack, and this time faced off against Saur. However, before that fight could conclude, it was interrupted by a pack of Diglett crossing, and later Bruno's Elite Four comrades Lorelei and Agatha.
A while later, Onix fought Bill and Lt. Surge on Cerise Island. He uses it this time to battle Red again. Onix was used to carry Red and the others off of Cerise Island as it was collapsing.