Gustav Mahler was a renowned Austrian composer and conductor of the late 19th and early 20th centuries. He is best known for his symphonies, which are often considered to be among the most powerful and emotionally charged works of the Romantic era. Mahler's music is characterized by its use of complex harmonic structures, extended tonal ranges, and large-scale forms. He also wrote several operas, choral works, and songs. Mahler's influence on the development of classical music has been profound, and his works remain popular today.