William Paats (b. Friedrich Wilhelm Paats Hantelmann, January 12, 1876, Rotterdam – d. August 28, 1946, Asunción) was a Dutch sports instructor.
Often regarded as "the father of Paraguayan football", Paats' family moved to Asunción, Paraguay in 1894. At that time, Williams was 18 years old and soon noticed the lack in the formal practice of any sport in Paraguay.
After a few years, he became a physical education instructor at the Escuela Normal school in Asunción. In one of his trips to Buenos Aires, he bought a football (ball) and brought it back to Paraguay; and soon after he started teaching the practice of football to his students. The popularity of football in Paraguay rose immediately, and small tournaments where held at the Plaza de Armas. Due to the success and enormous interest of the people, Paats decided to found the first Paraguayan football club, and so on July 25 of 1902 Olimpia Football Club was born.
Paats was also a founding member of the Asociación Paraguaya de Fútbol (Paraguayan Football Association) in 1906 and served as President of the mentioned organization from 1909 to 1910. He also promoted and taught the practice of other sports disciplines such as cricket, tennis, swimming and rowing. His passion for sports and social activities led him to found the social and sports club Sajonia in 1921 and the Touring Club Paraguayo in 1924. He also served as a consul for the Netherlands until 1935.
Paats died on August 28, 1946, in Asunción, leaving his legacy as one of the most important sports personalities in Paraguay.