A rock opera is a collection of rock music songs with lyrics that relate to a common story. Rock operas are typically released as concept albums and are not scripted for acting, which distinguishes them from operas, although several have been adapted as rock musicals. The use of various character roles within the song lyrics is a common storytelling device. The success of the rock opera genre has inspired similar works in other musical styles, such as rap opera.
In an early use of the term, the July 4, 1966, edition of RPM Magazine (published in Toronto) reported that "Bruce Cockburn and Mr [William] Hawkins are working on a Rock Opera, operating on the premise that to write you need only 'something to say'."
Colin Fleming of The Atlantic described The Story of Simon Simopath (1967) by British psychedelic band Nirvana as an "early foray into the rock opera sub-genre". Neil Strauss of The New York Times wrote that S.F. Sorrow (1968) by The Pretty Things is "generally acknowledged as the first rock opera". Although Pete Townshend denied taking any influence from S.F. Sorrow, critics have compared The Who's Tommy to it. Scott Mervis of the Pittsburgh Post-Gazette wrote that, although Tommy was not the first rock opera, it was the first album to be billed as such.Tommy would go on to influence On and On, a rap opera by The Fat Boys and American Idiot, a punk rock opera by Green Day. In an effort to appeal to more modern audiences, opera companies have welcomed more pop and rock influences. The resulting rock operas have met varying degrees of success as the worlds of high art and low art mix.
In Russian music, the term zong-opera (?-) is sometimes used, since the first Soviet-Russian rock-opera Orpheus and Eurydice was described with this term, though the term "rock-opera" was already known in the Soviet rock music circles.
A rock opera that experienced commercial recording and Broadway success is Jesus Christ Superstar, written by Andrew Lloyd Webber and Tim Rice, and in respect of which Lloyd Webber said "the piece was written as a rock album from the outset and set out from the start to tell the story through the music itself." 
According to Fleming, rock operas are more akin to a cantata or suite, as they are not usually acted out. Similarly, Andrew Clements of The Guardian called Tommy a subversively-labeled musical. Clements states that lyrics drive rock operas, which makes them not a true form of opera. Responding to accusations that rock operas are pretentious and overblown, Pete Townshend wrote that pop music by its very nature rejects such characteristics and is an inherently simple form. Townshend said that the only goal of pop music is to reach audiences, and rock operas are merely one more way to do so.Peter Kiesewalter, on the other hand, said that rock music and opera are "both overblown, massive spectacles" that cover the same themes. Kiesewalter, who was originally not a fan of opera, did not think the two styles would mix well together, but his modernized operas with rock music surprised him with their popularity at the East Village Opera Company.
Rock operas are usually recorded and performed on albums by the artists themselves, but they can also be performed on the stage, such as Rent, which played on Broadway. This usage has also courted controversy; Anne Midgette of The New York Times called them musicals with "no more than the addition of a keyboard and a drum set".