Base Ball Bear (ベースボールベアー ) is a Japanese rock band from Tokyo that formally began in 2002, although the members assembled in the autumn of 2001. The band, which was initially named Planet, was formed for a one-time performance at a high school culture festival, but they decided to continue playing due to how well they were received at the festival and how much fun they were having. Base Ball Bear made its major debut in early 2006 with EMI Music Japan. Their style influences include Japanese indie rock bands Number Girl and Supercar, and British rock bands such as Oasis. The band has been noted for the "nostalgic" feel of band leader Yūsuke Koide's lyrics, often about teenage life and memories. They are also known for their contributions to the soundtrack of the movie Linda Linda Linda (in which female bassist Shiori Sekine had a leading role) and performing the themes to the anime series Toshokan Sensō and Ōkiku Furikabutte.

The band's former name, Planet, most likely came from a Supercar song of the same name. Their current name also derives partially from a song name. Koide thought of Japanese singer Chocolat's song "Base Ball and Elvis Presley", and suggested the name "Base Ball". Guitarist Yuasa thought it would be better if they added one more word to it, and the rest of the band agreed. They eventually settled on the word "bear".