Little Busters! (リトルバスターズ!, Ritoru Basutāzu!) is a Japanese visual novel developed by Key. It was released on July 27, 2007 for Windows PCs and is rated for all ages. Little Busters! is Key's sixth game, along with other titles such as Kanon, Air, and Clannad. An adult version of the game titled Little Busters! Ecstasy was released on July 25, 2008 for Windows, unlike Kanon and Air, which were first released with adult content and then had later versions with such content removed. Ecstasy was later ported to the PlayStation 2, PlayStation Portable, PlayStation Vita, PlayStation 3, and Nintendo Switch with the adult content removed under the title Little Busters! Converted Edition. An English version for Windows was released on Steam in 2017. The story follows a group of childhood friends (Riki Naoe, Rin Natsume, Kyousuke Natsume, Masato Inohara and Kengo Miyazawa) now attending high school called the Little Busters, as they decide to form a baseball team. Riki, who is diagnosed with narcolepsy, is tasked to recruit more girls in preparation for a baseball game, and he bonds with each of them on account of their internal conflicts. Meanwhile, Rin gets mysterious letters from her cat Lennon to complete various tasks to learn the "secret to this world".

The gameplay in Little Busters! follows a branching plot line which offers pre-determined scenarios with courses of interaction, and focuses on the appeal of the six female main characters by the player character, which increases to nine in Ecstasy. There are additional minigames added into the gameplay, such as battle sequences that resemble fighting games or baseball batting practice, which serve to give the characters experience, obtain accessories to use during battle, and improve their statistics. Both Little Busters! and Ecstasy ranked as the best-selling PC game sold in Japan for the time of their release, and Ecstasy would go on to sell over 100,000 units. Key went on to produce an adult spin-off called Kud Wafter in June 2010, which expanded on the scenario of Kudryavka Noumi, one of the heroines from Little Busters! and Ecstasy.

There have been 14 manga adaptations based on Little Busters! and Ecstasy published by ASCII Media Works, Kadokawa Shoten and Ichijinsha. Comic anthologies, light novels and art books were also published, as were several music albums. There have been two Internet radio shows hosted by the voice actors of Rin and Kyousuke Natsume and Kudryavka Noumi. J.C.Staff produced two anime television series and an original video animation series between 2012 and 2014.