You catch deoxys at birth island.
Go to birth island.
There are sadly no special events to catch Deoxys in Sapphire. You HAVE to trade a Deoxys caught in an event from FireRed, LeafGreen, or Emerald.
Anything tbh you can defeat the Pokemon league again or catch other rare Pokemon:)
You must get a ticket from a Nintendo Event that takes you to Birth Island.
First you got to catch him in Pokemon leafgreen or fire red and trade. Or you can use a gameshark. it lets you catch all the Pokemon from bulbasaur to deoxys.
Where you catch Deoxys
You would need to use an Action Replay or transfer it from Pokemon Emerald, FireRed, or LeafGreen, for it is impossible to catch Deoxys in any location in Pokemon Diamond, Pearl, and Platinum.
You can't catch Deoxys in the wild or a special place. But if you got it in Pokemon FireRed, LeafGreen, Sapphire, Ruby, or Emerald you can migrate Deoxys in the Pal Park in the Kanto region in Fuchsia City.You cannot obtain Deoxys legitimately in Pokémon SoulSilver. You must take advantage of an Event in Pokémon Emerald, FireRed, or LeafGreen to go to Birth Island using an Aurora Ticket, and catch it there, then use the Pal Park to transfer it to SoulSilver. Alternatively, you can cheat.
kau sakai kau bodoh p.s don be a cheater
you have to get it in a event and you cant get it in Pokemon leafgreen or firered
you have to get more then 45 gym to catch legendary Pokemon! deoxys is a legendary Pokemon