The Cartier Santos is the watch first made for aviator Alberto Santos-Dumont in 1904.
Santos-Dumont asked his friend Louis Cartier for a watch that could be read while flying. Cartier developed a wristwatch with a square case, exposed screws and a leather strap, making it practical to consult without removing a pocket watch.
The design became commercially available in 1911 and is widely regarded as one of the earliest purpose-designed men's wristwatches. Its square case and visible bezel screws remain defining features.
It is sometimes confused with the Cartier Tank, another famous Cartier model introduced later in 1917. The Santos is specifically associated with aviation pioneer Santos-Dumont.