The Mahler Chamber Orchestra is a professional touring chamber orchestra founded by Claudio Abbado and former members of the Gustav Mahler Youth Orchestra in 1997.

The MCO appears throughout the year in about 60–70 concerts and performances. It consists of 45 musicians from 20 different nations. Its activities include concerts, opera projects, chamber music as well as CD recordings. Strong artistic links have been established with Daniel Harding (principal guest conductor 1998–2003, music director 2003–2008, principal conductor 2008–2011 and conductor laureate since 2011) and Claudio Abbado. The MCO has had stable residencies in Ferrara (Ferrara Musica, founder: Claudio Abbado) and Lucerne (Lucerne Festival). The first concert and founding residency of the MCO began on 21 November 1997 in Landshut, Germany.

The MCO's repertoire reaches from baroque to contemporary music. The MCO is a free-financed orchestra without any state support. Sponsors are, therefore, required to maintain the orchestra.