The Messa da Requiem is a musical setting of the Catholic funeral mass (Requiem) for four soloists, double choir and orchestra by Giuseppe Verdi. It was composed in memory of Alessandro Manzoni, whom Verdi admired, and is therefore also referred to as the Manzoni Requiem. The first performance, at the San Marco church in Milan on 22 May 1874, conducted by the composer, marked the first anniversary of Manzoni's death. It was followed three days later by the same performers at La Scala. Verdi conducted his work at major venues in Europe.

Verdi composed the last part of the text, Libera me, first, as his contribution to the Messa per Rossini which he had begun after Gioachino Rossini had died already contained the music that later begins the Dies irae sequence.

Considered too operatic to be performed in a liturgical setting, the Requiem is usually given in concert form; a performance lasts around 90 minutes. Musicologist David Rosen calls it "probably the most frequently performed major choral work composed after Mozart's Requiem".

After Gioachino Rossini's death in 1868, Verdi suggested to his publisher Ricordi that a number of Italian composers collaborate on a Requiem in Rossini's honour. He began the effort by submitting the concluding movement, the Libera me. During the next year a Messa per Rossini was compiled by Verdi and twelve other famous Italian composers of the time. The premiere was scheduled for 13 November 1869, the first anniversary of Rossini's death, but on 4 November, nine days before the premiere, the organising committee abandoned it. Verdi blamed this on the scheduled conductor, Angelo Mariani. He pointed to Mariani's lack of enthusiasm for the project, although in fact the conductor had been a part of the organising committee and did his best to support Verdi, this episode marked the beginning of the end of their friendship. The composition remained unperformed until 1988, when Helmuth Rilling premiered the complete Messa per Rossini in Stuttgart, Germany, presented at festivals and recorded.

On 22 May 1873, the Italian writer and humanist Alessandro Manzoni, whom Verdi had admired all his adult life and met in 1868, died. Upon hearing of his death, Verdi resolved to complete a Requiem—this time entirely of his own writing—for Manzoni. Verdi traveled to Paris in June, where he commenced work on the Requiem, giving it the form we know today. It included a revised version of the Libera me originally composed for Rossini.

The Requiem was first performed in the church of San Marco in Milan on 22 May 1874, the first anniversary of Manzoni's death, as part of a church liturgy. Verdi himself conducted, and the four soloists were Teresa Stolz (soprano), Maria Waldmann (mezzo-soprano), Giuseppe Capponi (tenor) and Ormondo Maini [it] (bass).

As Aida, Amneris and Ramfis respectively, Stolz, Waldmann, and Maini had all sung in the European premiere of Aida in 1872, and Capponi was also intended to sing the role of Radames at that premiere but was replaced due to illness. Teresa Stolz went on to a brilliant career, Waldmann retired very young in 1875, but the male singers appear to have faded into obscurity. Also, Teresa Stolz was engaged to Angelo Mariani in 1869, but she later left him.

The Requiem was repeated at La Scala three days later on 25 May with the same soloists and Verdi again conducting. It won immediate contemporary success, although not everywhere. It received seven performances at the Opéra-Comique in Paris, but the new Royal Albert Hall in London could not be filled for such a Catholic occasion. In Venice, impressive Byzantine ecclesiastical decor was designed for the occasion of the performance.