Shaft Inc. (stylized as SHAFT; Japanese: 株式会社シャフト, Hepburn: Kabushiki-gaisha Shafuto), also known as Shaft Animation Studio, is a Japanese animation studio founded in 1975 and headquartered in Suginami, Tokyo. Since 2004, the studio's productions and staff have been broadly influenced by director Akiyuki Shinbo, whose visual style and avant-garde cinematography are featured in works including Hidamari Sketch (2007), Sayonara, Zetsubou-Sensei (2007), the Monogatari series (2009–present), Puella Magi Madoka Magica (2011), Nisekoi (2014), and March Comes In like a Lion (2016).

Shaft was founded as a yūgen-gaisha on September 1, 1975, by ex-Mushi Production employee Hiroshi Wakao. Much of the company's early work was sub-contracting work for larger animation studios, which includes credits to cel painting and color coordination work, such as with Brave Raideen (1975–76), and occasionally credits as an assistant production studio for projects including Pierrot's Urusei Yatsura: Only You (1983). A large portion of the company's early painting work was contracted under Sunrise productions.

In 1984, Shaft was sub-contracted by studio Zuiyo to animate the Elves of the Forest television series, marking the company's first project as a primary animation studio. Not until 1987, however, with the release of the Yume kara, Samenai original video animation (OVA), did the studio release its first wholly-original production. In the same year, the studio produced the first episode of the Taiman Blues: Naoto Shimizu-hen OVA series.

For the next several years, the company returned to sub-contracting work based on animation production services rather than its painting services, such as with the Mushi Production film Ushiro no Shoumen Daare (1991). In 1995, the studio moved to producing full-length series, starting with Juuni Senshi Bakuretsu Eto Ranger. By this time, several directors and animators had joined the studio, such as Toshimasa Suzuki and Kenji Yasuda; however, one of the most important series in the company's early history was an outsourcing contract they took on in 1996: Legend of Crystania: The Chaos Ring, which began the studio's relationship with director Ryūtarō Nakamura and studio Triangle Staff. The second episode of the OVA series was outsourced to Shaft, and both Nakamura and Triangle Staff's president (Yoshimi Asari) visited Shaft while delivering the episode's storyboard. Mitsutoshi Kubota, a studio color designer turned production manager at the time, met with the two, and from then they would collaborate on several more projects together, such as Shaft producing an episode of Nakamura and Triangle Staff's Kino's Journey television series, and Nakamura later directing a television series and Kino's Journey film at the studio.

In 1998, Radix produced a 26-episode adaptation of Kia Asamiya's manga Silent Möbius; and although produced as a Radix production, Shaft was contracted as an outsourcing company for the entire series, and according to Kubota served as the production site for the series (rather than Radix). Shaft was also responsible for selecting the staff, and chief director Hideki Tonokatsu worked from the studio. Nobuyuki Takeuchi left Studio Giants in the early 90s, and Shaft offered him a seat at the studio as a freelancing animator; and for Silent Möbius, he took on the role of "animation director" (not referring to the correction of drawings). Kubota felt that Takeuchi would eventually play a central role in Shaft's works succeeding the series, and he eventually became an integral part of many of the productions made with Shinbo.

Shaft entered co-operations with studios Gainax and TNK around 2000. The first of the productions under these co-operations was Mahoromatic (2001) and its sequel Mahoromatic: Something More Beautiful (2002–03), both with Gainax and under the direction of Hiroyuki Yamaga. 2002 was also the release of the studio's production with TNK, G-On Riders. In 2003 and 2004, the studio produced an adaptation of the visual novel Popotan, and later This Ugly yet Beautiful World, an original series co-produced with Gainax and director Shouji Saeki. The development of This Ugly yet Beautiful World began when members of Mahoromatic said that they wanted to do another work with the team, which included both the voice actors and staff members. While searching for scriptwriting and directing staff to work on the project, Saeki and Gainax producer Hiroki Satou mentioned that it would involve much of the Mahoromatic staff to those they invited, such as director Shin Itagaki and writer Sumio Uetake.

In 2004, Wakao was succeeded as Shaft's representative director by Kubota, though he remained a chairman on the studio's board. After watching The SoulTaker (2001) and Le Portrait de Petit Cossette (2004), both works directed by Akiyuki Shinbo, Kubota decided that he wanted to work with Shinbo to create a uniquely identifiable brand for the studio. In October 2004, the studio animated its first production with Shinbo as director, Tsukuyomi: Moon Phase, and he began serving as an executive director and mentor to the studio's staff.

Shaft's final co-production with Gainax came in 2005 with He Is My Master. The same year saw the first animated production under the influence of "Team Shinbo", a director trio consisting of Shinbo, Shin Oonuma, and Tatsuya Oishi, who played a vital role in the studio's early stylistic decisions. Shinbo had invited both Oonuma and Oishi to direct episodes under him having seen their work under him on previous projects outside of Shaft. The next two years also saw the release of Rec (2006) and Kino's Journey: Country of Illness -For You- (2007), the aforementioned series directed by Ryūtarō Nakamura, which would be the last series produced by Shaft not to feature any involvement by Shinbo for more than a decade.