The Symphony No. 1 in D major by Gustav Mahler, often known by its nickname Titan, was written between 1884 and 1888.

The symphony is written for an orchestra consisting of four flutes, two piccolos, four oboes, a cor anglais, three clarinets, a bass clarinet, a bassoon, a double bassoon, seven French horns, four trumpets, three trombones, a tuba, two sets of timpani, a bass drum, cymbals, a triangle, a tambourine, a harp and string instruments (typically sixteen first violins, sixteen second violins, twelve violas, twelve cellos and eight double basses).

In its final form, the symphony has four movements:

1. Langsam, Schleppend (Slowly, dragging)
2. Kräftig bewegt (Moving strongly) - a Ländler
3. Feierlich und gemessen (Solemnly and measured) - a funeral march based on the children's song "Frère Jacques"
4. Stürmisch bewegt (Moving stormily)

Originally, there was an additional movement, known as the Blumine, between the first and second movements of the piece as it now stands. It seems probable that this movement was originally written for Mahler's incidental music for Joseph Scheffel 's play Der Trompeter von Säckingen (1884), which, the Blumine aside, has since been lost. Mahler discarded this movement in 1894 after the first three performances of the work, and it was not discovered again until 1966 when Donald Mitchell unearthed it. The following year, Benjamin Britten conducted the first performance of it since Mahler's time at Aldeburgh. The symphony is almost never played with this movement included today, although it is sometimes heard separately.

Under this original five-movement scheme, the work was envisioned by Mahler as a large symphonic poem, and he wrote a programme to describe the piece. It was divided into two parts, the first consisting of the first two movements of the symphony as it is now known plus the Blumine, and the second consisting of the other two movements. The programme was influenced in large part by the novelist Jean Paul, whose novel Titan gave the piece its later nickname.

The work includes a number of themes from Mahler's song cycle Lieder eines fahrenden Gesellen (1883-85).

The piece was first published in 1898, and in 1906 an arrangement by Bruno Walter for piano four hands (two players at one piano) was published.

Premieres

• World premiere: November 20, 1889, Budapest, conducted by the composer. The work was poorly received.
• English premiere: October 21, 1903, London as part of a Proms concert, conducted by Henry Wood.
• American premiere: December 16, 1909, New York City, conducted by the composer.