De Rossi announced the gift during an episode of The Ellen DeGeneres Show on Thursday.
Her donation to the Dian Fossey Gorilla Fund will create a permanent home in Rwanda for the organization that has been protecting endangered mountain gorillas for 50 years.
DeGeneres said in a statement Thursday that she is “beyond excited” about the opportunity to work with the group. She said de Rossi “knew the exact right gift to give me.”
DeGeneres has been an animal-rights activist for many years. People for the Ethical Treatment of Animals named her “woman of the year” in 2009.
Fossey wrote Gorillas in the Mist. She died in 1985.
DeGeneres’ actual birthday is on Jan. 26.