Alexander Ferdinand, 3rd Prince of Thurn and Taxis, full German name: Alexander Ferdinand Fürst von Thurn und Taxis was the third Prince of Thurn and Taxis, Postmaster General of the Imperial Reichspost, and Head of the Princely House of Thurn and Taxis from 8 November 1739 until his death on 17 March 1773. Alexander Ferdinand served as Principal Commissioner at the Perpetual Imperial Diet in Frankfurt am Main and Regensburg for Charles VII, Holy Roman Emperor, Francis I, Holy Roman Emperor, and Joseph II, Holy Roman Emperor from 1 February 1743 to 1745 and again from 1748 until 1773.

The Princely House of Thurn and Taxis is a family of German nobility that is part of the Briefadel. It was a key player in the postal services in Europe during the 16th century, until the end of the Holy Roman Empire in 1806, and became well known as the owner of breweries and commissioner of several castles. The family has resided in Regensburg since 1748 with their seat at St. Emmeram Castle from 1803. The family is one of the wealthiest in Germany, and the current head of the House is Albert, 12th Prince of Thurn and Taxis.