Les Misérables (/leɪ ˌmɪzəˈrɑːb(lə)/; French pronunciation: ​[le mizeʁabl(ə)]), colloquially known as Les Mis or Les Miz (/leɪ ˈmɪz/), is a sung-through musical adapted from French poet and novelist Victor Hugo's 1862 novel of the same name by Claude-Michel Schönberg (music), Alain Boublil and Jean-Marc Natel (original French lyrics), and Herbert Kretzmer (English lyrics). The original French musical premiered in Paris in 1980 with direction by Robert Hossein. Its English-language adaptation by producer Cameron Mackintosh has been running in London since October 1985, making it the longest-running musical in the West End and the second longest-running musical in the world after the original Off-Broadway run of The Fantasticks.

Set in early 19th-century France, Les Misérables is the story of Jean Valjean, a French peasant, and his desire for redemption after serving nineteen years in jail for having stolen a loaf of bread for his sister's starving child. Valjean decides to break his parole and start his life anew after a bishop inspires him by a tremendous act of mercy, but he is relentlessly tracked down by a police inspector named Javert. Along the way, Valjean and a slew of characters are swept into a revolutionary period in France, where a group of young idealists attempt to overthrow the government at a street barricade in Paris.

The musical opened as a pre-Broadway tryout at the Kennedy Center's Opera House in Washington, D.C. on 27 December 1986. It ran for eight weeks through 14 February 1987.

The musical then premiered on Broadway on 12 March 1987 at The Broadway Theatre. Colm Wilkinson and Frances Ruffelle reprised their roles from the London production.   The $4.5 million production had a more than $4 million advance sale prior to its New York opening.

The show underwent further tightening, namely with improved sewer lighting and the incorporation of the Javert suicide scene effect. A New York Times report consisted of the following: "The transfer from London to the United States has prompted further modifications. 'We are taking this opportunity to rethink and perfect, to rewrite some details which probably no one else will see, but which for us are still long nights of work,' Mr. Boublil says. 'There are things that nobody had time to do in London, and here we have a wonderful opportunity to fix a few things. No one will notice, perhaps, but for us, it will make us so happy if we can better this show. We would like this to be the final version.'"   Two songs were deleted—the complete version of Gavroche's song "Little People" and the adult Cosette's "I Saw Him Once". A short section at the beginning of "In My Life" replaced "I Saw Him Once". The lyrics in Javert's "Stars" were changed. It now ended with the line, "This I swear by the stars!", while the London production and cast recording ended with the repeated line, "Keeping watch in the night".

The original Broadway cast included Colm Wilkinson as Jean Valjean, David Bryant as Marius, Judy Kuhn as Cosette, Michael Maguire as Enjolras, Frances Ruffelle as Éponine, Braden Danner as Gavroche, Donna Vivino as Young Cosette, Jennifer Butt as Madame Thénardier, Leo Burmester as Thénardier, Randy Graff as Fantine, Terrence Mann as Javert, and Chrissie McDonald as Young Éponine.