In a picture posted on micro-blogging site Twitter, Gaga is seen scrapping up her shaved hairstyle onto the top of her head to reveal the inking, which a fan had designed for her, reports contactmusic.com.
Daniel, who owns King Seven Tattoo parlour in Copacabana, said: "Gaga came to me and said she wanted a tattoo that looked like something done in a prison - edgy, grey, I suppose a bit scary."
"She wanted a design that a fan had given her, the word 'Rio' where the letter 'I' was the Christ. She told me she wanted it to look like a prison tattoo, not a nice design, a bit shadowy.
"'Like something done in prison,' was the term she used,” Daniel added.