Maria Theresia Ahlefeldt (born Princess Maria Theresia of Thurn and Taxis, [full German name: Maria Theresia, Prinzessin von Thurn und Taxis] 16 January 1755 in Regensburg, Free Imperial City of Regensburg, Holy Roman Empire – died 20 December 1810 in Prague, Kingdom of Bohemia, Austrian Empire) was a member of the House of Thurn and Taxis and a Princess of Thurn and Taxis by birth and a member of the Ahlefeldt Danish noble family and Countess of Ahlefeldt-Langeland through her marriage to Ferdinand, Count of Ahlefeldt-Langeland. Maria Theresia was a Danish (originally German) composer. She is known as the first female composer in Denmark.

Maria Theresia was the eldest child and daughter of Alexander Ferdinand, 3rd Prince of Thurn and Taxis (1704–73) and his third wife Princess Maria Henriette Josepha of Fürstenberg-Stühlingen (1732–72). She was a younger half-sister of Karl Anselm, 4th Prince of Thurn and Taxis and niece of Maria Augusta of Thurn and Taxis.

She grew in a cultural environment at the princely court in Regensburg. Maria Theresia was engaged to Prince Joseph of Fürstenberg 1772–76 until her affair with Prince Philip of Hohenlohe. In 1780, she fled arrest after having married the Danish noble Ferdinand, Count of Ahlefeldt-Langeland (1747–1815) against the will of her family.

In 1780, Maria Theresia's spouse was marshal at the court of Ansbach, where she was active in the amateur theatre. In 1792–94, her spouse was marshal of the Danish court and director of the Royal Danish Theatre. Maria Theresia composed music for several ballets, operas, and plays of the royal theatre. She moved to Dresden in 1798 and lived from 1800 until her death in Prague.

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