Ulrich Schmidl or Schmidel (1510 in Straubing - 1579 in Regensburg) was a German Landsknecht, conquistador, explorer, chronicler and councilman. Schmidl was, beside Hans Staden, one of the few Landsknechts who wrote down their experiences.
Schmidl was the son of a wealthy merchant, and received a good education. He entered military service and took part 1534 as a Landsknecht under Pedro de Mendoza in an expedition to today's Argentina (Río de la Plata). He also accompanied Juan de Ayolas on his first trip in quest of provisions, and afterward went with Ayolas in his expedition up Paraguay River, and was one of the soldiers that were left with Domingo Irala in charge of the vessels in Puerto la Candelaria (modern Fuerte Olimpo). When Cabeza de Vaca was deposed in April 1544, Schmidel sustained Irala, who was the new governor, and in 1546 accompanied him in his expedition to Peru as far as the foot of the Andes, where he was despatched with Nuño de Chaves to President La Gasca. He accompanied Irala on his last unfortunate expedition of 1550.
He became a founder of Buenos Aires. His journey led him across the Río Paraná and Río Paraguay and into today's Paraguay, where he helped to found Asunción. From there he undertook several expeditions in the Gran Chaco, which led him into southeast Bolivia.