The 27-year-old singer announced in a statement that she will now be known as Lily Rose Cooper, reported Us magazine.
In the statement from her publicist, Lily also hinted she is working on new music. "It's great to work at my own pace, with no commitments other than to make music. I'm excited to be heading back into the studio."
Lily and Sam married on June 11, 2011 and the couple welcomed their first child, daughter Ethel Mary, on November 25, 2011.
In July, a source confirmed that Lily is pregnant with her second child. "She's pregnant but it's early. Lily doesn't want to talk about it yet," the source said.
The singer had previously said she was retiring from music and had no plans to make another album after the release of her second, It's Not Me, It's You, in 2009.