In each generation, there is typically at least one group of Legendary Pokémon that form a trio. Each Trio is seemingly subject to another Legendary Pokémon.
- Articuno, Zapdos and Moltres – The Legendary Birds, ruled by Lugia.
- Mew, Mewtwo, and MechaMew2 (live only) - The Mew Trio, ruled by Mew itself.
- Regice, Regirock and Registeel – The Legendary Golems, ruled by Regigigas.
- Groudon, Kyogre and Rayquaza – The Weather Trio. The master of this trio is in fact, Rayquaza itself.
- Uxie, Azelf and Mesprit – The Lake Trio, ruled by Arceus.
- Dialga, Palkia and Giratina – The Creation Dragons, ruled by Arceus.
- Reshiram, Zekrom and Kyurem: The Tao Dragons, ruled by Kyurem itself.
- Cobalion, Terrakion, and Virizion: Three Pokémon based on the titular characters of the novel The Three Musketeers. Out of these swords of justice, Cobalion is the oldest and wisest and is considered their leader.
- Keldeo: The fourth member of the Swords of Justice, thus making them a quartet.
- Tornadus, Thundurus, and Landorus: Based on three Japanese gods known as kami, with Tornadus based on Fujin, the god of wind, Thundurus on Raijin, the god of thunder, and Landorus on Inari, the fertility god. Landorus is the master of this trio.