Wagner began composing the music during a vacation in Teplitz in the summer of 1843 and completed the full score on 13 April 1845 the opera's famous overture, often played separately as a concert piece, was written last.

The sources used by Wagner therefore reflected a nineteenth century romantic view of the medieval period, with concerns about artistic freedom and the constraints of organised religion typical of the period of Romanticism. This confusion (which explains why Tannhäuser is referred to as 'Heinrich' in the opera) does not fit with the historical timeline of the events in the opera, since the Singers' Contest involving von Ofterdingen is said to have taken place around 1207, while Tannhäuser's poetry appeared much later (1245–1265). Wagner also knew of the work of another contemporary, Christian Theodor Ludwig Lucas, whose Über den Krieg von Wartburg of 1838 also conflated the two legends. Ludwig Bechstein wove together the two legends in the first volume of his collection of Thuringian legends, Der Sagenschatz und die Sagenkreise des Thüringerlandes (A treasury of the tales of Thuringian legends and legend cycles, 1835), which was probably the Volksbuch to which Wagner refers to in his autobiography. The legend of Tannhäuser, the amorous crusading Franconian knight, and that of the song contest on the Wartburg (which did not involve Tannhäuser, but the semi-mythical minnesinger Heinrich von Ofterdingen), came from quite separate traditions. Other possible sources include Friedrich de la Motte Fouqué's play Der Sängerkrieg auf der Wartburg and Eichendorff's Das Marmorbild (The Marble Statue, 1819). In Heine's sardonic essay Elementargeister (Elemental spirits), there appears a poem about Tannhäuser and the lure of the grotto of Venus, published in 1837 in the third volume of Der Salon. Heinrich Heine had provided Wagner with the inspiration for Der fliegende Holländer and Wagner again drew on Heine for Tannhäuser. To this Wagner added material from Hoffmann's story, from Serapions-Brüder (1819), describing a song contest at the Wartburg castle, a castle which featured prominently in Thuringian history. Tieck's tale, which names the hero 'Tannenhäuser', tells of the minnesinger-knight's amorous adventures in the Venusberg, his travels to Rome as a Pilgrim, and his repudiation by the pope. Hoffmann's story, Der Kampf der Sänger (The Singers' Contest). According to his autobiography, he was inspired by finding the story in 'a Volksbuch (popular book) about the Venusberg', which he claimed 'fell into his hands', although he admits knowing of the story from the Phantasus of Ludwig Tieck and E.

Wagner wove a variety of sources into the opera narrative.

Dich teure halle wagner