Side by Side by Sondheim is a musical revue featuring the songs of composer Stephen Sondheim. Its title is derived from the song "Side by Side by Side" from Company.

The musical had its origins when David Kernan was asked by Cleo Laine and her husband John Dankworth to put together a revue as a benefit for The Stables, a theatre they owned in Wavendon. Kernan contacted director Ned Sherrin and suggested that they do a revue of Sondheim material. Producer Cameron Mackintosh saw the benefit revue, which featured Millicent Martin, Julia McKenzie, Kernan, and Sherrin as the narrator, and agreed to produce it.

In the TV documentary Cameron Mackintosh: The Music Man, Mackintosh admits that he never saw the benefit performance, but Christopher Biggins did, and Mackintosh went on Biggins' recommendation.

The musical is in the form of a revue, with various sections tied together by being from a particular Sondheim musical, or having a common theme, and all of it is tied together by the Narrator. He explains what show the songs are from, and in some cases provides background on why a song was written. He also notes comparing and contrasting Sondheim themes for the audience. As the cast enters, they sing "Comedy Tonight", and then "Love Is in the Air"; the Narrator explains that the latter song was the original opener for A Funny Thing Happened on the Way to the Forum, but was dropped in favor of the more explicit lyrics of "Comedy Tonight". The Narrator notes that a theme that Sondheim has explored in many of his works is marriage, which introduces the next set of songs. Next are the unknown songs, one cut and one from a television program ("I Remember"). The medley from Company follows, and Act 1 closes with Follies, with the Narrator pointing out the different musical styles Sondheim has used in these songs, such as Vaudeville ("Buddy's Blues"). The female trio sing "You Could Drive a Person Crazy" as the act ends.

Songs included have varied from production to production; the following is the song list from the original Broadway production

The revue had its première on May 4, 1976, at London's Mermaid Theatre, where it ran for 59 performances. It subsequently transferred to Wyndham's Theatre, and then the Garrick for a total of 806 performances. Ned Sherrin directed, but Sondheim also worked with the cast and made many suggestions. Millicent Martin, Julia McKenzie, David Kernan, and Sherrin comprised the original cast.

Hal Prince produced the Broadway version, and persuaded Actors' Equity Association to allow the original British cast to transfer with the show. The production, again directed by Sherrin, opened on April 18, 1977, at the Music Box Theatre, and later transferred to the now-demolished Morosco Theatre. Lighting design by Ken Billington. Between the two venues, it ran for 384 performances and six previews. It is one of the few shows to have the distinction of its entire cast being nominated for Tony Awards (Best Featured Actor in a Musical and Best Featured Actress in a Musical). A subsequent 1978 U. S. national tour starred Martin, Larry Kert, Barbara Heuman, and Hermione Gingold as the Narrator.

The Australian production opened 21 September 1977 at Canberra Theatre, and subsequently toured to Sydney, Melbourne, and Adelaide. The cast included Jill Perryman, Geraldene Morrow, and Bartholomew John, with Noel Ferrier was the Narrator. John Laws was featured as the Narrator for the Sydney season, as well as on the cast album. The Australian cast recording was released by RCA in 1978.