Ignjat Nathan Fischer (18 June 1870, Zagreb – 19 January 1948, Zagreb) was a Croatian architect who was active in Zagreb during the first half of the 20th century.^[1][2]

Fischer was born in Zagreb to a Croatian-Jewish family.^[2][3][4] His father Samuel was a prominent construction engineer.^[2][5][6][7] Fischer studied in Vienna and Prague.^[2]

In his early stage he was one of the major architects who introduced the Vienna Secession in Croatian architecture. During that phase he created several impressive designs, such as a house Rado at Strossmayer Square 7 in 1897, sanatorium in Klaićeva Street known for its V-based ground plan in 1908, and the building of the deanery and the institute of pathology at the Medical Faculty of Šalata in 1912.^[2][8]

During the Interwar period, Fischer designed in the spirit of late modernism, historicism and, modestism. His greatest achievements are the forestry Academy building in Mažuranić Square 5 in 1920, the head office of City Savings Bank of Zagreb on Ban Jelačić Square in 1922–1925 (upgraded in 1931), and modern house Arko at Dolac Market.^[2][9]

The full extent of Fischer's work is not known with certainty. Recent research discovered a number of architectural designs that were previously not attributed to him, most notably the building of the Croatian Parliament in the St. Mark's Square.^[2][6] In Zagreb, he had a large studio where he designed up to forty different buildings.^[2]

Fischer was a member of Croatian Freemasonry.^[2][10] He was married to Helena (née Egersrodfer) with whom he had two daughters, Ivana and Marija Magdalena. Events before and during World War II affected his health.^[2] His daughter Ivana recalled that her "father was imprisoned even when he was 70 years old, because he was a Jew. As a result of those persecutions he became seriously ill and died in 1948."^[6] Fischer was buried at the Mirogoj Cemetery.^[11][12]

• Ivana Fišer (daughter)