First produced: 1978

Billy Bishop Goes to War is a musical written by John MacLachlan Gray with Eric Peterson about the exploits of First World War flying ace William Avery "Billy" Bishop. Since its premiere in 1978, the musical has been staged across Canada and in the United States and Europe. It remains one of the most popular Canadian musicals.

Billy Bishop Goes to War was written by composer John MacLachlan Gray in collaboration with actor Eric Peterson and performed by the same duo. It premiered on 3 November 1978 at the Vancouver East Cultural Centre. Peterson played 18 different characters, including Billy Bishop; Gray accompanied at the piano and sang. Their production toured widely in 1980–82 in Canada and also was seen in 1980 in Washington, DC; on Broadway (Morosco Theatre) and off-Broadway (Theatre de Lys) in New York; at the Edinburgh Festival; and in Los Angeles. It was staged in 1981 at the Comedy Theatre in London's West End.

A second Canadian production, with Cedric Smith (as Bishop et al.) and the pianist Ross Douglas, toured in 1980–81. Independent productions have been mounted in several US cities and in Europe, and new Canadian productions continued through the 1980s and 1990s, for example, at the 1987 Charlottetown Festival. The play continues to be staged, for example, at the Atlantic Theatre Festival (2000), Vancouver's Chan Centre for the Performing Arts (2008) and Saskatoon’s Persephone Theatre (2010). In November 2020, the musical was staged at the Highland Arts Theatre in Sydney, Cape Breton.

In 1998, John MacLachlan Gray and Eric Peterson revised Billy Bishop to portray the older Bishop looking back on his life; they also added one song. This production toured nationally with the authors in their original roles. The two made a second revision in 2009, rewriting the ending to reveal Bishop at the end of his life. This production premiered at Toronto's Young Centre for the Performing Arts in 2009; directed by Soulpepper Theatre Company’s Ted Dykstra, it once again featured Gray and Peterson in their original roles. It was staged by Soulpepper in 2017 as well.

A cast recording with Peterson and Gray was issued by Tapestry (GD-7372) in 1979; a recording of the revised musical was made at the Grand Theatre (London, Ontario) in 1999. The libretto was published by Talonbooks (Vancouver) in 1981.Billy Bishop was produced in 1982 for TV in Scotland by the BBC. A German version, Billy Bishop Steig Auf, also exists. A movie version featuring Gray and Peterson was released in 2011.

The musical brought Gray the 1981 Los Angeles Drama Critics' Award, the 1982 Chalmers Canadian Play Award, and the 1983 Governor General's Award for drama, as well as an ACTRA award for best television program. Billy Bishop Goes to War remains one of the most popular Canadian musicals.