What nationality was the inventor of the international language Esperanto?

Ludwik Lejzer Zamenhof (15 December 1859 – 14 April 1917), was a Polish ophthalmologist and the inventor of the international language Esperanto, the most widely-used constructed international auxiliary language in the world.

Zamenhof first developed the language in 1873 while still in school. He grew up fascinated by the idea of a world without war. He believed that this could happen with the help of a new international auxiliary language. The language would be a tool to gather people together through neutral, fair, equitable communication. He successfully formed a community that continues today despite the World Wars of the 20th century. Also, it has developed like other languages, through the interaction and creativity of its users.