While she got ready for the big night, "he was watching," Theron, 38, told PEOPLE at Fame & Philanthropy Post Oscar party.
"I got my first 'mama pretty' tonight, so it was a slam-dunk for me," said the actress. "I'm very happy right now," she said, adding that motherhood is "really good."
From the looks of it, her relationship with Sean Penn seems to fall in the same category.
Jason Kempin / Getty
Despite being swarmed by fans, the pair looked quite happy and comfortable together. Not that this appears to be anything new: on their recent Mexican getaway, the stars "were inseparable," an eyewitness told PEOPLE. "They looked completely enamored with each other."