- Profession: Rabbi (First Rabbi of Jihlava).
- Relation to Mahler: Teacher.
- Correspondence with Mahler:
- Born: 1827.
- Died: 16-10-1912 Jihlava. Aged 85.
- Buried: Jewish cemetery (U Cviciste Nos. 12/2070, Trainingsgelande), Jihlava.
- School German Gymnasium (Hluboka street Nos. 1/109, Nonnengaschen 608) (1869-1877).
- Synagogue (Benesova street, Obere Sacher Gasse).
- Mahler's Religion teacher.
- After a half year at school Mahler is 31/51. At the end of the first year he is 22/49.
- Mahler received his best mark in Religion (Mosaic) from Dr. Unger: Excellent.
- 1877: Mahlers results were no longer quite so respectable but Rabbi Unger was still satisfied with his charge in matters of the Jewish religion. Year 1877.
In 1860, the first rabbi came to Jihlava. Joachim Jakob Unger (1826-1912) came from a small village near Kosice - spent his entire life in Jihlava for the development of the Jewish community (rabbinic photographs in the archive). He built the synagogue and in 1869 the Jewish cemetery, then behind the town. There are 1340 graves in that cemetery, and Rabbi Unger is buried there. On the night of March 30, 1939, the synagogue was burned, then the ceremonial hall of the cemetery.
Schillerova (Benesova street).