The answer to this question depends on your dog's breed, coat type, and activity level.
Dogs with thick coats, such as Labrador Retrievers and Golden Retrievers, don't need to be bathed as often as dogs with thin coats, such as Poodles and Greyhounds.
Dogs with short coats can be bathed less often than dogs with long coats.
Dogs who are active outdoors and get dirty often may need to be bathed more often than dogs who are mostly indoor dogs.
A good rule of thumb is to bathe your dog every 2-4 weeks. However, you may need to bathe your dog more or less often depending on the factors mentioned above.
If your dog starts to smell, has mats in their fur, or is covered in dirt or mud, then it's time for a bath.
Avoid getting shampoo in your dog's eyes.