Born in Aachen, Ritter received his doctorate in educational psychology at the University of Munich in 1927. Continuing his studies in child psychology, Ritter received his doctorate in medicine at University of Heidelberg in 1930.
In 1936, Ritter was appointed to head the newly created Eugenic and Population Biological Research Station of the Reich Health and Sanitation Office. By 1941, his research about the Roma led to Axis forces implementing a policy of genocide against them. Ritter then became chief of the newly created Criminal Biological Institute of the Reich Security Head Office. Ritter's team of researchers included a number of younger race scientists, including Eva Justin, Adolf Würth, and Sophie Ehrhardt.
After the war, Ritter was employed as a psychologist for the Frankfurt Public Health Office, along with Eva Justin. In 1948, at the behest of Roma survivors of the Porajmos, the Frankfurt prosecutor's office opened an inquiry into Ritter's Nazi-era activities. The case was closed in 1950, on the grounds of insufficient evidence.
- Schmidt-Degenhard, Tobias Joachim (2008). Robert Ritter 1901 - 1951. Zu Leben und Werk des NS-"Zigeunerforschers". Tübingen.