Marek Janowski (born 18 February 1939 in Warsaw) is a Polish-born German conductor.

Janowski grew up in Wuppertal near Cologne, after his mother traveled there at the start of World War II to be with her parents. His father disappeared in Poland during the war.

Janowski has served as music director in Freiburg and at the Dortmund Opera conducting the Dortmunder Philharmoniker, the latter from 1973 to 1979. From 1983 to 1987 he was principal conductor of the Royal Liverpool Philharmonic Orchestra. He served as Kapellmeister of the Gürzenich Orchestra in Cologne, from 1986 to 1990. Earlier, in 1984, he became the music director of the Orchestre Philharmonique de Radio France (then called the Nouvel Orchestre Philharmonique) in Paris, a position he held until 2000. From 2000 to 2009, Janowski served as Principal Conductor of the Monte-Carlo Philharmonic Orchestra. He was also Principal Conductor of the Dresden Philharmonic from 2001 to 2004.

From 2002 through 2016, Janowski was chief conductor of the Berlin Radio Symphony Orchestra, initially with a contract for life with the orchestra at the time. In the 2005/06 season, Janowski began his tenure as Artistic and Music Director of the Orchestre de la Suisse Romande (OSR), with an initial contract of five years. In September 2008, his contract with the OSR was extended to 2015. However, in January 2010, in a change to the September 2008 contract extension, Janowski and the OSR mutually agreed on the scheduled conclusion of his directorship of the OSR after the 2011-2012 season.

Janowski had served as chief conductor of the Dresden Philharmonic from 2001 to 2003. In September 2018, the Dresden Philharmonic announced the re-appointment of Janowski as its chief conductor, effective with the 2019-2020 season, with an initial contract of 3 seasons.

In the USA, beginning in 2005, Janowski served as one of the conductors in a "triumvirate" of conductor leadership with the Pittsburgh Symphony Orchestra (PSO), with Sir Andrew Davis and Yan Pascal Tortelier, providing artistic guidance for the orchestra in the absence of a single music director. This arrangement ended in 2008 after the accession of Manfred Honeck as the PSO's music director. Janowski now holds the Otto Klemperer Guest Conductor Chair with the PSO. He has recorded the four symphonies of Johannes Brahms with the PSO.

Janowski has made a number of operatic recordings, including the first digital recording of the complete Ring Cycle of Richard Wagner between 1980 and 1983 for RCA, with the Staatskapelle Dresden. He and that orchestra had earlier made the first recordings of Die schweigsame Frau by Richard Strauss, in 1976 for EMI, and of Euryanthe by Carl Maria von Weber, in 1974 for EMI, with Jessye Norman and Nicolai Gedda singing the lead roles. Another operatic first recording was of Krzysztof Penderecki's The Devils of Loudun with the Hamburg State Opera, shortly after he led the world premiere of the work in 1969.