Inflatable castles (also called bouncy houses, bouncy castles, jumping castles, moon bounces, moonwalks, or closed inflatable trampolines) are temporary inflatable structures and buildings and similar items. They are rented for backyard and block party functions, school and church festivals and village fetes and used for recreational purposes. The growth in the use of such devices has led to a rental industry that includes inflatable slides, inflatable water slides, obstacle courses, and giant games, carnival games, and more.

Inflatable castles have been suggested as having some therapeutic value for children with certain sensory impairments, similar to ball pits.

American engineer John Scurlock is credited as inventor of the modern inflatable tent design, in 1958. Scurlock, a plastics specialist who taught at Tulane University and worked for NASA, later also invented the Space Walk safety air cushion used by stunt performers and fire brigades responding to high-rise fires. According to his family, he was inspired in the late 1950s while designing inflatable tent covers for tennis courts. Scurlock's original design was known as the "Space Pillow", it had very little in common with modern bounce houses. In 1958 he also founded Space Walk Inc. In the 1980s the family business operated an indoor amusement park, The Fun Factory, in Metairie, LA, and today continues to rent heavy-duty inflatables for occasions ranging from county fairs to children's birthday parties. The idea to rent inflatables for parties is attributed to Scurlock's wife Frances, who was running a rental business by 1969.

Bob Regehr is also credited for inventing the bouncy house in 1968, under the brand name Moon Walk.

As part of the space-themed toy trend sparked by the space race, 'The Moon Walk', a closed inflatable trampoline with a plastic roof designed for children's safety, was available for mail order in the 1975 Neiman Marcus catalog.

The original bouncy house was essentially an air pillow with a roof, but the hundreds of modern models include inflatable waterslides, basketball gyms, a game in which players attempt to knock each other over with a large inflatable wrecking ball, and characters licensed from multimedia franchises such as Frozen. Thousands of companies now rent inflatable castles in the United States. The market has also diversified to include lighter retail designs. By 2014, the industry was estimated to be worth $100 million.

The world's largest inflatable castle, The Big Bounce America, was certified in 2018 at 1,062.252 square metres (11,433.99 ft²). It includes multiple zones, such as ball pits, an obstacle course, a slide, a basketball court, and a DJ booth. It was designed as an inflatable theme park for all ages, and started touring the United States in the summer of 2019 as a traveling festival.

With adult play a growing trend, bouncy castle rentals have also seen increased popularity at weddings.