Wilde, 26, is best known for her work on TV's "House, M.D." Her film credits include "Tron: Legacy," "Cowboys & Aliens" and "The Change Up."
In addition to having royal connections, Ruspoli, 35, is a documentary filmmaker and musician.
"They have been living apart after trying for quite some time to make their relationship work," a source told People.com Tuesday.
Wilde's representative confirmed the separation to People.com, but offered no other details about it.