Thea Stilton is a fictional character from the popular children's book series created by Geronimo Stilton. She is a journalist and the sister of Geronimo, known for her adventurous spirit and love for mystery. Thea is the leader of a group called the Thea Sisters, which includes her friends who help her solve various challenges and uncover secrets. The series features engaging stories that combine friendship, teamwork, and problem-solving. Thea and her friends travel to different locations, learning valuable lessons along the way. The books are designed to inspire young readers and encourage a love for reading through colorful illustrations and relatable characters.