Gaga, 26, took to her Little Monsters website to share the sad news and she posted a picture of her radical new hairstyle, reported Ace Showbiz.
In the photo, Gaga appears to have cut off her long hair and shaved the back of her head, and she reveals her new look is a tribute to Richardson's mum.
"I did it for you Terry. I'm sorry about your mummy. She has Princess Die (late British royal, Diana, Princess of Wales), but were (we are) all princess high," Gaga posted.
Richardson, who collaborated with Gaga on a recent picture book, posted his own tribute to his mother on his online blog, sharing a picture of her and writing, "RIP Annie Lomax, my mom 1938-2012."