Otto Lanz (14 October 1865, in Steffisburg – 23 March 1935, in Amsterdam) was a Swiss surgeon. He studied medicine at several universities in Europe, and in 1890–92 served as an assistant to Theodor Kocher at the University of Bern. Afterwards, he took an extended study trip to Berlin, Naples and London, and in 1894 settled as a docent of surgery at Bern. In 1902 he was named a professor of surgery at the University of Amsterdam. He is remembered for his surgery of the thyroid gland and his work associated with appendicitis. In the field of plastic surgery, he introduced mesh grafting in 1907.