Elisabeth "Sissy" Waldheim (née Ritschel; 13 April 1922 – 28 February 2017) was the wife of Kurt Waldheim, the UN Secretary-General and President of Austria.

She was the First Lady of Austria from 1986 to 1992.

She was born in Vienna as the eldest of three sisters to Wilhelm Ritschel and his wife Hildegard. Wilhelm's father (her grandfather) was a military official in the imperial army. After the fall of the Habsburg empire, he became an entrepreneur. His daughter Elisabeth was named after the former Austrian empress Elisabeth and she gained her nickname of "Sissy".

Waldheim decided to study law at University of Vienna, where she first met Kurt Waldheim. On 19 August 1944, in the middle of the Second World War, the couple married in Vienna. Their first daughter, Lieselotte, was born in 1945. According to her husband's New York Times obituary, "[s]he was an ardent Nazi who before the war had renounced her Roman Catholic faith and joined the League of German Maidens, the young women’s equivalent of the Hitler Youth. She applied for Nazi Party membership as soon as she was old enough, and was accepted in 1941".

Waldheim gave up her own job in order to support her husband's diplomatic and political career. He became the Foreign Minister of Austria and UN Secretary General. In 1986, he was elected President of Austria and she became Austria's First Lady. The couple had three children: daughter Lieselotte Waldheim-Natural is working at the United Nations, daughter Christa Waldheim-Karas became an artist (she is married to Othmar Karas, Austrian Member of the European Parliament), and son Gerhard Waldheim is an investment banker. She spoke German, English and French. Elisabeth Waldheim died on 28 February 2017 at the age of 94.