Gustav Mahler (7 July 1860 – 18 May 1911) was a Bohemian-born Austrian composer and conductor. He was best known during his own lifetime as one of the leading orchestral and operatic conductors of the day. He has since come to be acknowledged as among the most important late-Romantic/early-Modernist composers, although his music was never completely accepted by the musical establishment of Vienna while he was still alive. Mahler composed primarily symphonies and songs; however, his approach to genre often blurred the lines between orchestral Lied, symphony, and symphonic poem

--------------------

Here's his Wikipedia page:

http://en.wikipedia.org/wiki/Mahler