Philipp, Prince of Eulenburg and Hertefeld, Count of Sandels (12 February 1847 – 17 September 1921) was a diplomat of the German Empire who achieved considerable influence as close friend of Wilhelm II, German Emperor.

The (also called the Harden–Eulenburg affair) a public controversy surrounding a series of courts-martial and five civil trials regarding accusations of homosexual conduct, and accompanying libel trials, among prominent members of Kaiser Wilhelm II's cabinet and entourage during 1907–1909.