how long is a well-known trademark valid? Well-known trademark is not an honor, but a legal concept. Who is it? Case identification? Yes, it was only famous in that case at that time, so there is no question of validity. It can be said that there is no question about the validity period of a well-known trademark, and it can also be said to be permanent. There is no accurate concept about the protection period of a well-known trademark, because the validity period of a trademark after registration is 1 years. Even if it is a well-known trademark, it needs to be renewed after 1 years. If it is not renewed, the well-known trademark will also be cancelled. Others can also apply for this trademark again. Recommended reading: well-known trademarks are prohibited.