Friedrich Karl August (German: Friedrich Karl August Fürst zu Waldeck und Pyrmont; 25 October 1743 – 24 September 1812) was Prince of Prince of Waldeck and Pyrmont from 1763 to 1812.

He was the second son of Karl August, Prince of Waldeck and Pyrmont and Countess Palatine Christiane Henriette of Zweibrücken-Birkenfeld.

He stayed on for one and a half years in Lausanne and made his Grand Tour through Italy and France.

Friedrich Karl August rented Waldecker troops to Great Britain in 1775 to fight in the American Revolutionary War.

[1] The principality was divided 1805, his brother George was given Pyrmont, and Friedrich Karl August stayed with Waldeck.