Do you need to beet the elite four catch chimecho in Sapphire?

You do not need to beat the Elite Four to catch Chimecho in Pokémon Sapphire.

Here's why:

* Chimecho is found in the Sootopolis City: This location is accessible before you challenge the Elite Four.

* Chimecho is a rare encounter: It is found in the water surrounding the city, but it has a very low encounter rate.

Therefore, you can catch Chimecho without needing to beat the Elite Four first.