There will be 18 gyms in Pokémon Sword and Shield - Dot Esports

Split between a minor and major league.

Pokémon Global News

How many gyms will there be in Pokémon Sword and Shield?

Pokémon Sword & Shield will feature 18 gyms, exp share changes, and more - LootPots

Pokemon Company clarifies that there are NOT 18 gyms in Sword and Shield - Dexerto

Ash Ketchum To Battle A New Gym Leader Not From Pokémon Sword & Shield

People focused way too much on the tree screenshot. This games art-style really carries this game visually imo. : r/PokemonSwordAndShield

Debunked) 18 Gyms in Pokemon Sword and Shield!?

Pokemon Company clarifies that there are NOT 18 gyms in Sword and Shield - Dexerto

18 Gyms in Pokémon Sword & Shield!? + More Game Informer Details! (No HMs, Autosave, & More!)

All 18 Galar Gym Leaders & Their NEW Signature Pokemon!

Pokemon Sword and Shield: Can I change my uniform when battling a gym?

All 18 Galar Gym Leaders & Their NEW Signature Pokemon!