Kidman adopted two children with ex-husband Tom Cruise and has two biological children with husband Keith Urban. She told CNN that her desire to have a family stemmed from her own "maternal instincts," which have been a "driving force" in her life since she was a young girl.
"I think because I've experienced motherhood in so many different ways," she said. "I've experienced adoption, birthing a child and I've experienced surrogacy. I'm like when it comes to it, I just wanna be a mama."
"I suppose my maternal instincts and drive has always been there since I was little ... and that's a huge driving force of who I am, which is why I probably played it out in so many different ways. I am a mother because I love being a mother."
Kidman plays Sue Brierley in the true story of an Australian woman who adopts a 5-year-old boy from India after he is separated from his family. The boy, Saroo, grows up, decides to search for his biological family and uses Google Earth to find them.
"As Sue said, there are so many facets to adoption," Kidman said. "There's women that adopt because that's what they've come to. There's women that adopt because that's the vision that they had, which was Sue. There's women that adopt because suddenly something happens in the family. Like in my family, my mother's cousin became her sister because her mother adopted her because her family passed away. So there are so many different ways in which adoption plays out, and I'm just glad to show one side of it."
For Kidman, the film, also starring Dev Patel and Rooney Mara, holds a very special place in her heart.
"I've made films that make philosophical statements or examinations of the human condition and all, but this for me is a film very much about life and about connection and the strengths of mothers," she said.
"Lion" hits theaters Friday.