Maria Appinger was born the daughter of an engineer in Nuremberg in 1903. She grew up together with five siblings and, after attending elementary school and a school for home economics, she lived initially with their parents. In 1928, she went to Berlin to train to become a nurse. After her training in the Protestant Johannesstift and short periods of nursing work, she took up a post at the Wittenau Hospital in Berlin in 1934.
In late 1939, Maria Appinger, who had already joined the National Socialist Party in 1932, was transferred to T4 through the emergency service obligation (Notdienstverpflichtung). During »Aktion T4«, she escorted patients to the killing centres of Grafeneck and Pirna-Sonnenstein and oversaw them during their examination before they entered the gas chamber. At times, she was also employed in the Niedermarsberg »children's ward«. In 1942/43, she worked in the T4 research department in Heidelberg and in the institutions of Bernburg and Hadamar. She retired from the service of the T4 in 1943 and returned to Berlin. Until the end of the war, she worked as an assistant in the public administration. For her participation in the patient killings, T4 issued her with a good »performance certificate«.
At the end of 1947, Maria Appinger was arrested, but acquitted in the Grafeneck trail by the Schwurgericht (criminal court composed of three professional and two lay judges that deals with the most serious crimes) in Tübingen in 1949.