Giannini has been with Nylon for the past three years. She previously worked for Spin.
Giannini is succeeding Michelle Lee, who is leaving the magazine.
“We’re thrilled to have an experienced editor like Melissa move into this role so we can ensure a seamless transition,” said Nylon CEO Paul Greenberg, in a statement. “She is the perfect person for the position, as she fully understands the NYLON brand with her tailored editorial background and time with the company specifically. At the same time, we thank Michelle for her superb work at Nylon and wish her the best.”