Henriette Mendel, Baroness von Wallersee (July 31, 1833 – November 12, 1891) was a German actress, and the mistress and, later, morganatic wife of Ludwig Wilhelm, Duke in Bavaria.

She was an actress at Darmstadt's Großherzoglich Hessisches Hoftheater when she and Ludwig Wilhelm, Duke in Bavaria fell in love.

He was the brother-in-law of Emperor Franz Joseph I of Austria, to whom his younger sister Elisabeth (Sissi) was married.

The couple's son Karl Emanuel was born on May 9, 1859, Henriette was created Freifrau von Wallersee on May 19, 1859, and the marriage occurred on May 28, 1859, in Augsburg, Bavaria, at which time her children became Freiin and Freiherr von Wallersee.

One year later, her widower, Duke Ludwig, married Barbara Antonie Barth, who had been created Baroness von Bartolf, on November 19, 1892.