William Mayer-Gross was born in the ancient Rhineland town of Bingen. He attended the Gymnasium in Worms and studied medicine in Heidelberg, Kiel and Munich. He took his final medical examinations in Heidelberg in 1912. He then became an assistant in the Heidelberg Psychiatric Clinic and in 1913 presented his doctoral thesis, which dealt with the phenomenology of abnormal feelings of felicity. On the outbreak of the First World War he was called up and served for a year on the Western front; he was then in 1915 assigned to duties in a base hospital where neurotic soldiers were being cared for.