The Nobel Prize-winning scientist who discovered radioactivity was Marie Curie. She was a pioneering physicist and chemist born in Poland and later naturalized in France. Curie's groundbreaking work in the late 19th and early 20th centuries led to her winning the Nobel Prize in Physics in 1903, shared with her husband Pierre Curie and Henri Becquerel, for their joint research on radiation phenomena. She later won a second Nobel Prize in Chemistry in 1911 for her discovery of the elements radium and polonium. Curie's remarkable achievements have made her a significant figure in the history of science, especially in the fields of radioactive studies and medical applications.