Creature suits are realistic costumes used to disguise a performer as an animal, monster, or other being. They are used in film, television, or as costumed characters in live events. Unlike mascots, they are often made with a high degree of realism. In contrast with prosthetic makeup, which is applied to an actor's skin, the wearer is not normally visible outside their movements controlling the costume, although in some cases, part of the wearer's body is still visible (such as in the case of mermaids or other half-human monsters).

Creature suits have been used since before movies were invented. As part of his circus sideshow in London in 1846, P. T. Barnum had an actor wearing a fur suit of an "ape-man", and continued to dress actors in similar costumes as attractions. They were used starting from the early days of film as practical effects, to represent animals that were too prohibitive to train or use, such as gorillas. Some films even tried to pass off costumes as real animals, which caused controversy.

The first foam rubber creature suit used in film was Gill-man, from the film Creature from the Black Lagoon, which released in 1954 and beat Godzilla by half a year. The suit, created by the film special-effects artist Don Post, was extremely hot when worn outside of the water, requiring actor Ben Chapman to be regularly hosed down, and difficult to see out of.

The success of Godzilla caused creature suits to be adopted in the Japanese tokusatsu genre as kaiju, or giant monsters. They were animated using the suitmation technique, combining slow-motion filming and miniature sets to make them appear larger than they really were.

Creature suit technology advanced during the latter half of the 20th century to include modern materials and animatronics integrated into the costume itself, increasing their realism. The animatronics were usually puppeteered by an operator with a remote control. However, their use dropped due to the advent of CGI, which was often cheaper to implement. For example, the suit used in the television series Harry and the Hendersons cost USD $1 million.

Nevertheless, despite the fluidity of CGI animals and monsters, purely visual effects are often panned, or, at least, not preferred by discerning film viewers. It is extremely difficult to mimic realistic lighting, leading to most CGI creatures and characters looking obviously fake when placed alongside real environments, especially if the film has a low budget and cannot afford sophisticated 3D modeling and rendering. Films such as Jurassic Park, which made heavy use of practical effects, including creature suits, remain well-regarded for their special effects, while CGI creatures quickly become dated as technology advances. This has led to the continued use of creature suits in modern-day films and commercials to provide additional realism, such as Hellboy and Star Wars: The Force Awakens.

In other instances, CGI and creature suits are combined, using green parts of the suit to chroma key them and add or remove appendages in post-production. This technique was used to hide suit actors' heads in the 2005 film Zathura: A Space Adventure, replace satyr creatures' legs in the 2005 film The Chronicles of Narnia: The Lion, the Witch and the Wardrobe, and to add facial expressions to the monsters in the 2009 film Where the Wild Things Are.

Creature suits have also been used in many live events and productions, such as the dinosaur suits used in Walking with Dinosaurs − The Arena Spectacular. They are also used in LARPs to represent monsters and other creatures that have to interact with players. In addition, they are sometimes used in hoaxes, such as Bigfoot sightings.