Théophile Alexandre Steinlen, 1859-1923, frequently referred to as just Steinlen, was a Swiss-born French Art Nouveau painter and printmaker.

Steinlen studied at the University of Lausanne before taking a job as a designer trainee at a textile mill in Mulhause in eastern France. In his early twenties he was still developing his skills as a painter when he and his new wife were encouraged to move to the artistic community in the Montmartre Quarter of Paris in 1882. Once there, Steinlen was introduced into the artistic crowd that led to his commissions to do poster art and other commercial enterprises.

In Paris, Steinlen worked as an illustrator for the journals Mirliton, Assiette au Beurre, Chat Noir, and Gil Blas, for which he produced over four hundred lithographs. As an artist he was not merely a commercial success but showed great sensitivity toward his subject matter. Besides illustrating advertisements for a variety of products, Steinlen was famous for his posters of cabaret and music hall performers.

He was very found of animals, especially cats, and often included them in his posters. Steinlen's cats proved so popular, in fact, that they became a trademark of his work.

Today, his works can be found at many important museums around the world including at the Hermitage Museum in St. Petersburg, Russia, and the National Gallery of Art in Washington, D.C., United States.

All the cats and dogs in this 1905 ad for Chéron Veterinary Hospital appear to be lovingly cared for by a very pretty young woman.