Dienstag aus Licht (Tuesday from Light) is an opera by Karlheinz Stockhausen in a greeting and two acts, with a farewell, and was the fourth of seven to be completed for the opera cycle Licht: die sieben Tage der Woche (Light: The Seven Days of the Week). It was begun in 1977 and completed from 1988 to 1991, to a libretto by the composer.

Dienstag is an opera for 17 solo performers (three singers, 10 instrumentalists, 4 dancer-mimes), actors, mimes, choir, orchestra, and electronic music. Tuesday is the red day of conflict between Michael and Lucifer (Stockhausen 1989b, 200).

As was the case for most of the operas in the Licht cycle, component sections of Dienstag were commissioned and composed separately, and given seriatim premieres. The first component of this opera was in fact the first part of the entire Licht cycle to be composed: Jahreslauf (Course of the Years), which became the first act of Dienstag, was originally written in 1977 as an independent piece for gagaku ensemble. Stockhausen finished it in Kyoto in the fall of 1977, and it was premiered by the Imperial Gagaku Ensemble at the Tokyo National Theatre on 31 October. This version is dedicated to Jaynee Stephens. A concert version for European instruments, with the slightly different title Der Jahreslauf (The Course of the Years), was performed in the Large Broadcasting Hall of the WDR, Cologne, on 10 February 1979. The day before the premiere, a studio recording was made for commercial release, and the same musicians participated in five staged performances of this act produced by the Paris Opera at the Opéra-Comique from 20 to 24 November 1979 (Stockhausen 1989a, 156). It was while working on this piece in Japan that the idea occurred to him of composing a seven-part cycle of operas, all based on a single, multi-layered musical formula (Kurtz 1992, 2). In the spring of 1991 Stockhausen added a narrative frame for Michael and Lucifer (Kurtz 1992, 236).