What was Niels Bohr's mother's maiden surname?

Niels Bohr’s mother’s maiden surname was Adler.

Bohr’s mother was Ellen Adler, daughter of David Baruch Adler, a prominent Danish Jewish banker and civic figure. She married Christian Bohr, a professor of physiology, and their son Niels was born in Copenhagen in 1885.

The surname is sometimes confused with names connected to Bohr’s scientific family. His father was Christian Bohr, while his brother Harald became a mathematician and Olympic footballer. Niels later married Margrethe Nørlund; Nørlund was therefore his wife’s family name, not his mother’s.

Ellen Adler’s background also places Bohr within Copenhagen’s educated and influential Jewish-Danish circles. Her father’s family helped shape the social setting in which Bohr grew up before he became one of the founders of modern atomic and quantum physics.