Several ways. First get a Rhydon. Rhydon evolves into Rhyperior.
Once you have a Rhydon the next step is to find a Protector (this is an item). You find a Protector in Mt Mortar.
Now you need to evolve Rhydon. Rhydon evolves when traded with a Protector attached. So the easiest way would be to trade with a friend and then trade back.
However if you don't have a friend there's a cool thing in Goldenrod City called the GTS. Either trade directly for a Rhyperior or trade for a Rhydon with a Protector attached (which is a rare thing to find and if you find it, 9 in 10 chances it will be for a Celebi, Deoxys or Rhyperior).
"But wait! I try to trade for a Rhyperior at the GTS but I can't find Rhyperior on the list!" That's because it hasn't been put in the Pokedex. To encounter a Rhyperior, challenge Blue to a rematch and he has a Rhyperior.
"How do you challenge Blue to a rematch?" get a massage from his sister in Pallet Town on the same Pokemon 5 days in a row. She gives massages between 3pm and 4pm. After 5 she gives you Blue's number and you can call him Sunday Night for a rematch.
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Rhyperior is a 4th generation Pokemon and therefore yo are not able to attain this in fire red. Diamond and Pearl however do have Rhyperior.
You cannot get Rhyperior in Pokemon emerald as he is only in Pokemon diamond and pearl.
You have to have a metal coat and give it to rhydon and ten trade it. dont do that trade a rhydon with a protector to get rhyperior
You can't get rhyperior in emerald because it didn't exist yet until diamond and pearl came out.
No