Marek Kopelent (Czech: [ˈmarɛk ˈkopɛlɛnt]; 28 April 1932 – 12 March 2023) was a Czech composer, music editor and academic teacher, who is considered to have been at the forefront of the "New Music" movement, and was one of the most-published Czech composers of the second half of the 20th century.

After studies in Prague, he worked as a music editor. In 1959 he became interested in European avantgarde music and incorporated its developments in his style. He received international recognition when his String Quartet No. 3 was performed at festivals throughout Europe. He co-founded and directed a contemporary music ensemble in Prague, Musica Viva Pragensis, and composed chamber music for them. He studied further for one year in West Berlin on a scholarship by Deutscher Akademischer Austausch Dienst. When he returned, politics had changed to censorship of contemporary music; he lost his job, and his music was banned. For 15 years, he worked as an accompanist at a music school, and composed pieces for foreign commissions that he could not hear being performed. In 1989, he was able to return, and was appointed professor of composition at the Academy of Fine Arts in Prague. He was chairman of the Czech section of the International Society for Contemporary Music.

His compositions focus on chamber music, concertante music, and vocal music from solo songs to oratorios, based on a wide range of texts from medieval to contemporary. He received international awards.