Marie Auguste was born on August 11, 1706. She grew up in the Austrian Netherlands and later moved to Frankfurt, where her family's wealth and economic interests were based. Her only brother was Alexander Ferdinand, 3rd Prince of Thurn and Taxis, whose son Karl Anselm would marry Marie Auguste's only daughter in 1753.
Marie Auguste was chosen as a bride for Karl Alexander, Duke of Württemberg-Winnental (later Duke of Württemberg) because of her Roman Catholic religion. They were married on May 1, 1727 in Frankfurt am Main. Despite their Catholicism, the couple's children were all raised in the Lutheran faith. They had four surviving children:
Their ten-year marriage was turbulent, and they were generally felt to be each other's match in every way (as both were masters of intrigue and secret diplomacy). He often used a trusted servant to spy on his wife to ensure that she would not interfere in government or criticize the Duke's ministers. After a particularly serious dispute in 1736, her husband even had her promise in writing to stay out of government affairs.
Marie Auguste's husband died suddenly on March 12, 1737 on the eve of his departure on a military inspection tour. This meant that their nine-year-old son Karl Eugen succeeded as Duke of Württemberg. After experiencing initial trouble from the regency council in trying to hold power for her son, she was finally successful on November 5, 1737. She was granted a large allowance and was recognized as co-regent with control over her son's education.
From 1739 to the following year, she had an affair with a captain in the army. Rumors of a possible pregnancy became so widespread that the privy council began an investigation; the captain was discharged and she was forced to stay in Brussels for five months (beginning in April 1740). Her exile removed her from direct power, especially when crucial policy decisions and preparations for her son's education were being made. For instance, she was unable to prevent a disastrous alliance with Prussia that would leave Württemberg exposed at the outbreak of the War of the Austrian Succession.