The Red Orb is an item (Key item from Gen III-V) that controls Groudon in the Hoenn region.
Ruby, Sapphire & Emerald
In Ruby, Sapphire and Emerald, the Red Orb appears and controls Groudon in Ruby, which Archie attempts to use to control Kyogre, but fails in doing so.
HeartGold & SoulSilver
In HeartGold and SoulSilver, it can also be obtained from Mr. Pokémon in both games and can be traded to it's counterpart to receive the Jade Orb to awaken Rayquaza in the Embedded Tower.
Omega Ruby & Alpha Sapphire
In Omega Ruby and Alpha Sapphire, the Red Orb becomes a standard item to accommodate the Primal Reversion of Groudon.
Red Orb's sprite from Gen III-V.