• English / United States: Millis Steel
• Japanese / Japan: ミリス·スティール
• Japanese (Romanized) / Japan: Miriss Steel
• Japanese (TL) / Japan: Miriss Steel

Millis Steel is a famous Pokémon bandit that was attempting to catch Diancie in order for it to make diamonds for her. Her father is Argus Steel. She worries about her fathers health as he eats too many chocolate.

She pretended to be looking out for Diancie when she rescued her from Team Rocket but she had been spying on Diancie to know when the right time was to attempt to capture it.

In the movie credits, she and her father are seen running a chocolate shop.