Marie Catherine Sophie, Comtesse d'Agoult (born de Flavigny; 31 December 1805 – 5 March 1876), was a French romantic author and historian, known also by her pen name, Daniel Stern.

[1] Marie was born in Frankfurt am Main, Germany,[2] with the full name of Marie Catherine Sophie de Flavigny, the daughter of Alexandre Victor François, Vicomte de Flavigny (1770–1819), a footloose émigré French aristocrat, and his wife Maria Elisabeth Bethmann (1772–1847), whose father was the German merchant and banker Johann Philipp Bethmann (1715–1793).

The young Marie spent her early years in Germany and completed her education in a French convent after the Bourbon Restoration.

From summer 1837 until autumn 1839 they travelled to Italy and Switzerland, staying successively in Bellagio, Milan, Venice, Lugano, Modena, Florence, Bologna and Rome.

It was these travels that inspired the composer to write his cycle of piano collections entitled Années de pèlerinage.