Sonic Team is a video game developer owned by the Japanese video game company Sega as part of its Sega CS Research and Development No. 2 division. Sonic Team is best known for its namesake long-running Sonic the Hedgehog series and games such as Nights into Dreams and Phantasy Star Online.

The initial team, formed in 1990, comprised staff from Sega's Consumer Development division, including programmer Yuji Naka, artist Naoto Ohshima, and level designer Hirokazu Yasuhara. The team took the name Sonic Team in 1991 with the release of their first game, Sonic the Hedgehog, for the Sega Genesis. The game was a major success and contributed to millions of Genesis sales. The next Sonic games were developed by Naka and Yasuhara in America at Sega Technical Institute, while Ohshima worked on Sonic CD in Japan. Naka returned to Japan in late 1994 to become the head of CS3, later renamed R&D No. 8. During this time, the division took on the Sonic Team brand but developed games that do not feature Sonic, such as Nights into Dreams (1996) and Burning Rangers (1998).

Following the release of Sonic Adventure in 1998, some Sonic Team staff moved to the United States to form Sonic Team USA and develop Sonic Adventure 2 (2001). With Sega's divestiture of its studios into separate companies, R&D No. 8 became SONICTEAM Ltd. in 2000, with Naka as CEO and Sonic Team USA as its subsidiary. Sega's financial troubles led to several major structural changes in the early 2000s; the United Game Artists studio was absorbed by Sonic Team in 2003, and Sonic Team USA became Sega Studios USA in 2004. After Sammy Corporation purchased Sega in 2004, Sonic Team was reincorporated to become Sega's GE1 research and development department. Naka departed during the development of Sonic the Hedgehog (2006), and Sega Studios USA was merged back into Sonic Team in 2008. The following decade was marked by Sonic games of varying reception, with head of studio Takashi Iizuka acknowledging that Sonic Team had prioritized shipping over quality.