There's no single answer here, it depends a lot on the breed, coat type, and how much time your dog spends outside.

• Short-haired breeds: Once every 4-6 weeks is usually plenty.
• Long-haired or double-coated breeds: Every 6-8 weeks, with regular brushing in between.
• Dogs with skin conditions: Follow whatever schedule your vet recommends, sometimes weekly with a medicated shampoo.
• Puppies: Less frequent bathing until their skin barrier matures, usually every 4-6 weeks max.

Bathing too often can strip natural oils and lead to dry, itchy skin, so more isn't always better.