"Colin the Caterpillar" is a chocolate roll cake sold by the major British multinational retailer Marks & Spencer. More than 15 million Colin the Caterpillar cakes have been sold since it was introduced in 1990.

Colin the Caterpillar is a chocolate sponge roll cake filled with chocolate buttercream and covered in a milk chocolate shell, with sugar-coated milk chocolate beans for decoration. The cake has a decorative face and feet made of white chocolate. The dessert is available in large and small sizes.

According to Marks & Spencer, it takes 38 people to assemble each cake from start to finish, and 8.4 tonnes (8,400 kg) of sugar coating are used each year for the decorative spots.

Initial success for sales of the cake has been attributed to the ongoing popularity of Eric Carle's children's picture book The Very Hungry Caterpillar (1969), and that a bestselling cookbook by Jane Asher, published the same year that the cake launched, also featured a recipe for a caterpillar birthday cake. Colin the Caterpillar has since become a staple of children's birthday parties, but is also popular with teens and adults.

In 2020, Marks & Spencer marked the cake's 30th anniversary by declaring Colin's birthday, Wednesday 26 August, as National Colin the Caterpillar Day.

Over the years, Marks and Spencer has produced several seasonal and limited edition variations on the original Colin the Caterpillar cake:

Similar caterpillar cakes are available in other rival retailers. These include:

Gluten and milk free versions are also available; Carl the Caterpillar from Tesco, Frieda the Caterpillar from Asda, and Eric the Caterpillar from Sainsbury's.