Cindy Lou Who is a fictional character from Dr. Seuss' storybook How the Grinch Stole Christmas!. She is depicted as a sweet little girl and serves as the tritagonist (third most important character) in the book and its adaptations

. In the 2000 live-action film adaptation, Cindy Lou Who was portrayed by actress Taylor Momsen, who later became known as the lead singer of the rock band The Pretty Reckless

. Additionally, "Cindy Lou Who" is the title of a 2023 song by Sabrina Carpenter, which is unrelated to the original character but shares the name

. In summary, Cindy Lou Who is primarily known as a beloved character from Dr. Seuss' Christmas story, famously portrayed by Taylor Momsen in the 2000 movie.