Pikachu is arguably the franchise's best-known Pokemon as a mascot, even getting its own game last year with Pokemon Let's Go Pikachu. Those who had a save file for this game could get a Pikachu in the new Pokemon Sword and Sword with a Gigantamax special form, but that would come at the cost of not being able to evolve it. You can still catch a wild Pikachu and evolve it, and this guide will tell you how to do it.
How to evolve Pikachu in Raichu
Since the very first Pokemon games with Red and Blue, Pikachu has had a different method of evolution than just leveling it up. You can level Pikachu up to level 99 and it will never evolve that way.
Instead, you'll need to use a special Evolution Stone to turn Pikachu into Raichu. The stone you will need is a thunder stone. This guide explains how to get one in Pokemon Sword and Shield.
Once you have acquired the Thunder Stone, go to your bag and select the Thunder item. Now you can look left and see the list of Pokemon in your party. Make sure Pikachu is in your party first. Once Pikachu is, select Pikachu with the stone, which should say compatible. If you accidentally grabbed the Pikachu from Let's Go here, it'll say Incompatible instead, so make sure you get the correct one.
Once you use the Thunder Stone on Pikachu, it will become Raichu. This cannot be transformed into Raichu's Alolan form like this, which you would have seen in Pokemon Sun and Moon. For this, you'll get the classic Electric Raichu type that most will recognize from Pokemon Sword and Shield.