Is it possible to catch Rayquaza on Pokemon Sapphire?
Yes it is possible. There is a guide on how to get it here at ign.com here is the link guides.ign.com/guides/496231. Rayquaza will be level 70 with an incredible arsenal of moves so be cautious and use good pokemon. I would suggest your Kyogre if you caught it but have it be a level 75 +. If you kill Rayquaza you do not have another chance so save in front of it before you battle with it. I would suggest a master ball if you have one.