Hugo Grotius was a lawyer, philosopher and writer from the Netherlands who lived in the 1600s. He wrote books about laws and justice, and argued that all people should be able to follow the idea of natural law and do what is fair and just, no matter what country they live in. He also wrote about freedom of religion and freedom of movement, meaning he thought people should be free to practice their religion and move freely around the world. He was a very important figure and is respected for his work today.