How do you catch Groudon and Kyogre?

Yes you can catch both of them in this game to find out where they are go to the walthroughs section or the hints section

What I would say first is that you can indeed catch them both.
Saying how would contain a little more detail. First, beat the E4. Then, go onto route 119 and go to the Weather Institute. In there, go to the second floor and talk to the scientist that gave you the Castform. He'll say that there's a drought on route xxx and if you go there, you should find a cave that was never originally there. Obviously, it's Terra Cave, where Groudon rests. Then, after you're done with Groudon, go back and talk to the same scientist. He'll then say that there is a rain pour on route xxx and if you go there, you should find a diving area that was never originally there. Obviously, it's Marine Cave, where Kyogre rests.

Go to the weather Institute and the man upstairs will tell you a Route. Go to it and try to find Tierra or underwater cave.

Please rate and verify this.

Yes you can catch them both. To find them, go to the Weather Center on route 119 and go to the second story. Talk to the scientist guy on the far left. He'll tell you that either there's a drought or heavy rains on a certain route. Go to that route and look for a cave. If it's heavy rains, the cave might be underwater. Enter the cave, go through a tunnel or two, and you'll find Groudon or Kyogre, depending upon the weather outside. The rain or sun will last awhile, so you'll have plenty of time to look, but it won't last forever, and it'll say the sun or rain is subsiding. But you can only access the caves once you've gotten Rayquaza to calm the two down in Sootopolis.

Ok after you beat the elite 4, go to the weather centre, the guy on the top floor will say there has been rain at either route 105,125,127 or129, go there and it will be raining, you should see a place where you can dive, dive and you go into a cave and kyogre will be there, it is lv 70

To get groudon do the same thing, he is also lv 70

I forgot how to catch them, but I know that you can indeed catch them both, my friend did that.

A guy in the Weather Institute tells you where you can catch them.

You can catch them both ater you beat the Pokemon leauge then go to the place you got castform then talk to the guy next to computer and he will tell you where to go

Yes, you can capture both.

Defeat the Pok�mon League and talk to the scientist on the second floor of the Weather Institute. He will tell you about a monsoon on Route 105, 125, 127, or 129. Go to that location and look for an unusual dive spot and descend. Resurface at the end of the path and go into the inner part of the cavern. At the end of the path is Kyogre.

Once you've defeated or captured Kyogre, go to the scientist again. This time he'll pinpoint a drought, which can be either on Route 114, 116, or 118. Go to that route and look for an unusual cave. Go into the inner chamber, where Groudon waits.

To get them beat the elite 4 then go to the weatther instatute and talk to sceintist on top floor than he tells you were he c's heavy suneshine and rain

You must trade them from Ruby, Sapphire or Emerald. And to be able to trade with these versions you must have obtained the Ruby and Sapphire gems.