Anastacia Lyn Newkirk ( AN-ə-STAY-zhə; born September 17, 1968) is an American singer-songwriter. Her first two studio albums, Not That Kind (2000) and Freak of Nature (2001), achieved chart success with the single "I'm Outta Love", "Not That Kind", "Paid My Dues" and "One Day In Your Life". Her third album, 2004's Anastacia, while her duet with Eros Ramazzotti, "I Belong to You (Il Ritmo della Passione)", was a success throughout Europe in 2006. After switching labels, she released her fourth studio album, Heavy Rotation, in 2008, followed in 2012 by the cover-album, It's a Man's World. She further released Resurrection (2014) and Evolution (2017) that included the single "Caught in the Middle". In 2023, she released an album of German songs translated into English entitled Our Songs.

Singing was Anastacia's third career-choice. She has disclosed several health issues, including Crohn's disease and two instances of breast cancer. In recognition of her charitable efforts in breast cancer awareness, Anastacia became the second woman ever to receive the Humanitarian Award at the GQ Men of the Year Awards, in 2013.