Ditto is a very popular Pokemon, and this one is no different than Sword and Shield. In this guide, we'll show you where to find transforming Pokemon.
Where to find Ditto in Pokemon Sword and Shield
Ditto on Outrage Lake, located on the map between Route 5 and Route 6. Unfortunately, you can't just head to Outrage Lake, as it is cut by a river. You will need to finish the sixth Gym Challenge and get a bike that can cross the water before you can go there.
The good news is that while Ditto isn't exactly a common spawn, it can be found on the earth world map and as a chance encounter in the grass in this area. If you see exclamation marks coming from the grass, you should investigate as it may be the very same idem you are looking for.
Another important thing to remember is that the weather affects what Pokemon will generate and Ditto will thankfully generate in any weather. Head to the Lake of Outrage when you can access it, then run around the area looking for spawns. If you can't find a Ditto, leave the area and come back to reset the spawns and try again.
If you need more help with Pokemon Sword and Shield, we have a number of guides that you might find useful. From how to use PC Box Link, how to change the nature of a Pokemon, and how to trade Pokemon.