Kaiserhofstraße 12 (published in English under the title The Invisible Jew)[1] is a memoir by the German author Valentin Senger (1918–1997), who was born in Frankfurt to Russian-born Jewish parents.

Originally published in German in 1978, it depicts his childhood at Kaiserhofstraße in central Frankfurt during the Weimar Republic and the Nazi era, and how his Jewish family survived the entire Nazi era undetected in the middle of Frankfurt with the help of several non-Jewish friends and neighbours at Kaiserhofstraße, sympathetic public officials, his mother's creativity and a good portion of luck.

The Sengers were liberal Jews who only occasionally attended the synagogue and who did not observe all customs of Judaism.

Valentin was circumcised, however, and the family maintained their contact with the city's Jewish institutions until the late 1930s.

When Valentin and his brother were conscripted into the army, the military doctor discovered that they were circumcised, but said nothing of it.