The aim of the article is to show the originality of a new genre of portrait opera, established by Philip Glass. In the operas composed in this genre one can find a combination of an innovative compositional technique and a dramatic structure with the unconventional form and content of the libretto, in which socio-political ideas and cultural contexts are introduced. These issues are presented in the article both against the background of Philip Glass's remaining operatic work and the development of American and European opera at the turn of the 20th and 21st centuries. In Philip Glass's rich operatic oeuvre, the genre of portrait opera is represented by seven operas. The first three operas that form the Trilogy: Einstein on the Beach (1976), “Satyagraha” (1979) and “Akhnaten” (1983) were described by the composer as portrait operas, but this genre is continued also in the later works: “Galileo Galilei” (2001), Kepler (2009) and “The Perfect American” (2013). The novelty of the portrait opera genre is expressed in several original genre assumptions adopted by the composer. These are: making the main characters famous historical figures who, thanks to their activities and visionary ideas, attracted societies in different epochs; strong exposure of the main character; the presence of social and political ideas in the libretto, and building acts on the juxtaposition of scenes, often resembling poetic images. The presence of political ideas occurs with uneven intensity in individual portrait operas. Two of them, the operas Satyagraha and “Akhnaten”, are political operas. In other operas, such as “Kepler, The Perfect American” and “Galileo Galilei”, political issues are only side -themes. Philip Glass's portrait operas feature also numerous and varied cultural contexts, such as the idea of multiculturalism (in “Satyagraha”) and the juxtaposition of chronologically inconsistent elements of different cultures in one work.