Marie-Adélaïde was born on 13 March 1753 at the Hôtel de Toulouse in Paris. Styled "Mademoiselle d'Ivoy" initially and, as a young girl, until her marriage, "Mademoiselle de Penthièvre" (derived from the duchy inherited by her father). The style of "Mademoiselle de Penthièvre" had been previoulsy borne by her sister Marie Louise de Bourbon (1751–1753) who died six months after Marie Adélaïde's birth. She was raised in a convent, the "Abbaye de Montmartre", overlooking Paris. 