Base Ball Bear is a Japanese rock band from Tokyo that made its major debut in 2006 with EMI Music Japan. Although assembled in autumn 2001, the band formally began in 2002, and started off with self-produced releases.

Their style influences include Japanese indie rock bands Number Girl and Supercar, and British rock bands such as Oasis. They have been noted for the "nostalgic" feel of band leader Yūsuke Koide's lyrics, often about teenage life and memories. Base Ball Bear are also known for their contributions to the soundtrack of the movie Linda Linda Linda (in which bassist Shiori Sekine had a leading role) and performing the themes to the anime series Toshokan Sensō, Ōkiku Furikabutte and Gintama.

The band, initially named Planet, was formed for a one-time performance at a high school culture festival, but decided to continue due to how well-received they were and the fun they had at the festival. The name Planet had likely come from the Supercar song of the same name, and the band's current name also derives partially from a song name. Koide had thought of Japanese singer Chocolat's song "Base Ball and Elvis Presley" and suggested the name "Base Ball". Guitarist Shohei Yuasa thought it would be better if one more word was added to it, and the rest of the band agreed, eventually settling on the word "bear".

In 2016, the band announced the departure of Shohei Yuasa and that they would continue with 3 members.