Cookie Monster is a popular Muppet character on the children's television show Sesame Street. He is best known for his voracious appetite and his famous eating phrases: "Me want cookie!", "Me eat cookie!", and "Omm nom nom nom" (said through a mouthful of food). He often eats anything and everything, including danishes, donuts, lettuce, apples, bananas, and inedible objects such as salt and pepper shakers, napkins, telephones, motorcycles, trucks, and the four letters in the word "food". Once, he even attempted to eat Guy Smiley and the petals and leaves off of Bert's flower costume in a Sesame Street Little Theater pageant. As evidenced by his name, however, his favorite food is cookies. Chocolate chip cookies are his favorite kind; oatmeal cookies are his second favorite. In a song in 2004, Cookie Monster revealed that, before he ate his first cookie, he believes his name was Sid.

He is known to have a mother, a younger sister, and an identically-designed cousin, who all share his characteristic blue fur and "googly eyes". He also has a father, who appeared in a Monsterpiece Theater sketch promoting energy conservation, water conservation and environmentalism. Both Cookie Monster's mother and father have his enormous appetite.