The Office is an American mockumentary sitcom television series based on the 2001–2003 BBC series The Office created by Ricky Gervais and Stephen Merchant and starring the former. Adapted for NBC by Greg Daniels, the show depicts the everyday work lives of office employees at the Scranton, Pennsylvania branch of the fictional Dunder Mifflin Paper Company, and aired from March 24, 2005 to May 16, 2013, with a total of nine seasons consisting of 201 episodes. The show was co-produced by Daniels' Deedle-Dee Productions, Reveille Productions (later Shine America) and 3 Arts Entertainment (although uncredited) in association with Universal Television. The original executive producers were Daniels, Gervais, Merchant, Howard Klein and Ben Silverman, with numerous others being promoted in later seasons.

Like the British original, the series was filmed in a single-camera setup without a studio audience or a laugh track, to mirror the look of an actual documentary. It debuted on NBC as a mid-season replacement and ended its nine-season run on May 16, 2013, with a two-part series finale. Its original main cast was Steve Carell, Rainn Wilson, John Krasinski, Jenna Fischer, and B. J. Novak. It experienced numerous changes to its ensemble cast during its run. Stars outside the original main cast include Ed Helms, Rashida Jones, Amy Ryan, Mindy Kaling, Craig Robinson, James Spader, Ellie Kemper, and Catherine Tate.

The Office received moderately positive reviews from critics (except for the pilot episode which received mixed reviews) during its relatively short first season of 6 episodes, a British television standard, but the following seasons, particularly Carell's performance, received significant acclaim from television critics as the show's characters, content, structure, and tone diverged considerably from the original British series. These seasons were included on several critics' year-end top TV series lists, winning several awards including a Peabody Award in 2006, two Screen Actors Guild Awards, a Golden Globe Award for Carell's performance, and five Primetime Emmy Awards, including one for Outstanding Comedy Series, in 2006. The eighth season was criticized for declining quality, with Carell's departure in season seven seen as a contributing factor. However, the ninth and final season ended the series with a generally positive response. The series finale, which originally aired on May 16, 2013, was viewed by an estimated 5.7 million viewers and garnered critical acclaim. In 2016, Rolling Stone named The Office one of the 100 greatest television shows of all time.

Greg Daniels adapted the British Office series for American television and served as the showrunner for the first four seasons. He then left the position when he co-created the comedy series Parks and Recreation with fellow Office writer Michael Schur and divided his time between both series. Paul Lieberstein and Jennifer Celotta were named the showrunners for the fifth season. Celotta left the series after the sixth season and Lieberstein stayed on as showrunner for the following two seasons. He left the showrunner spot after the eighth season for the potential Dwight Schrute spin-off, The Farm, which was eventually passed on by NBC. Daniels returned to the showrunner position for the ninth and final season. Other executive producers include cast members B. J. Novak and Mindy Kaling. Kaling, Novak, Daniels, Lieberstein and Schur made up the original team of writers. Kaling, Novak, and Lieberstein also served multiple roles on the series, as they played regular characters on the show, as well as wrote, directed, and produced numerous episodes. Credited with twenty-four episodes, Kaling is the most prolific writer among the staff. Ricky Gervais and Stephen Merchant, who created the original British series, are credited as executive producers and wrote both pilot and the third-season episode "The Convict". Merchant later directed the episode "Customer Survey", while Gervais appeared briefly in the episodes "The Seminar" and "Search Committee", reprising his role as David Brent from the British series.

Randall Einhorn is the most frequent director of the series, with 15 credited episodes. The series also had many guest directors, including Lost co-creator J. J. Abrams, Buffy the Vampire Slayer creator Joss Whedon, both of whom are fans of the series, and filmmakers Jon Favreau, Harold Ramis, Jason Reitman, and Marc Webb. Episodes have been directed by several of the actors on the show including Steve Carell, Rainn Wilson, John Krasinski, B. J. Novak, Ed Helms, Brian Baumgartner, Mindy Kaling and Paul Lieberstein.

Before the second episode airing, the writers spent time conducting research in offices. This process was used for Daniels' other series King of the Hill and Parks and Recreation. The pilot is a direct adaptation of the first episode of the original British series. Daniels chose to go this route because "completely starting from scratch would be a very risky thing to do" owing to the show being an adaptation. He had briefly considered using the idea for "The Dundies" as the pilot episode. After the writers knew who the cast was, they were allowed to write for the actors, which allowed the show to be more original for the following episode, "Diversity Day". Following the mixed reaction toward the first season, the writers attempted to make the series more "optimistic" and to make Michael Scott more likable. They also established the supporting characters of the series more, giving them relatable personalities. They also made the lights in the office brighter, which allowed the series to differentiate itself from the British series.

A common issue with the scripts, according to Novak, is that they tended to run too long for the regular 22-minute time slot, leading to several cuts. For example, the script for the episode "Search Committee" was initially 75 pages, which was 10 pages too long. A complete script was written for each episode; however, actors were given opportunities to improvise during filming. Fischer said, "Our shows are 100 percent scripted. They put everything down on paper. But we get to play around a little bit, too. Steve and Rainn are brilliant improvisers.". These improvisations led to a large number of deleted scenes with almost every episode of The Office, all of which are considered part of the show's canon and storyline by Daniels. Deleted scenes have sometimes been restored in repeats to make episodes longer or draw back people who have seen the episode before to see the bonus footage. In an experiment, a deleted scene from "The Return" was made available over NBC.com and iTunes, explaining the absence of a character over the next several episodes. Daniels hoped that word of mouth among fans would spread the information, but he eventually considered the experiment a failure.

According to Jenna Fischer, the series used an unusual casting process that did not involve a script. For example, the producers asked the actors several questions and they responded as the characters they were auditioning for. NBC programmer Kevin Reilly originally suggested Paul Giamatti to producer Ben Silverman for the role of Michael Scott, but the actor declined. Martin Short, Hank Azaria and Bob Odenkirk were reported to be interested in the part. Silverman offered the role to Ricky Gervais, who played David Brent in the British series, but he declined as he felt it would not make sense and did not want to move to the United States.