Therese Elisabeth Alexandra Förster-Nietzsche (10 July 1846 – 8 November 1935) was the sister of philosopher Friedrich Nietzsche and the creator of the Nietzsche Archive in 1894.

Förster-Nietzsche was two years younger than her brother. Their father was a Lutheran pastor in the German village of Röcken bei Lützen. The two children were close during their childhood and early adult years. However, they grew apart in 1885 when Elisabeth married Bernhard Förster, a former high school teacher who had become a prominent German nationalist and antisemite. Friedrich Nietzsche did not attend their wedding.

Förster-Nietzsche and her husband created an unsuccessful colony, Nueva Germania, in Paraguay in 1887. Her husband killed himself in 1889. Förster-Nietzsche continued to run the colony until she returned to Germany in 1893 where she found her brother to be an invalid whose published writings were beginning to be read and discussed throughout Europe. Adolf Hitler attended her funeral in 1935.

In the 1950s it was claimed by Nietzsche's new editors and translators such as Walter Kaufmann that Nietzsche's work had been falsely edited by Elisabeth to highlight racist and eugenicist themes, but this account has been the subject of debate in recent scholarship. An alternative theory exonerates Elisabeth and places the distortion of Nietzsche's works in the hands of the Nazis themselves.