How do you get Ho-Oh in Pokemon Sapphire?
Ho-Oh is unobtainable in the wild in Ruby or Sapphire without cheating. You will therefore need to trade for it from Pokémon Colosseum...or Fire Red, Leaf Green, or Emerald if you have access to the Mystic Ticket.
There are quite a few ways to get Ho-oh or Lugia in Pokemon Sapphire. Get the Mystic ticket in Emerald and trade them You can win a Ho-oh in Pokemon Colosseum for completing Mt Battle vs 100 with your story mode Pokemon, which you can then transfer to Sapphire Lugia is a shadow Pokemon in Pokemon XD Gale of Darkness, you can transfer it to Sapphire after you catch and purify it Cheat