Lauritz Lebrecht Hommel Melchior -often misspelled Melchoir- (March 20, 1890 – March 18, 1973) was a Danish, later American opera singer. He was the preeminent Wagnerian tenor of the late 1920s, 1930s, and 1940s, and has since come to be considered the quintessence of his voice type.

Born in Copenhagen, Denmark, the young Melchior was a boy soprano and amateur singer, before starting his first operatic vocal studies at the age of 18 in 1908.

In 1913 Melchior become a professional opera singer, making his debut in the baritone role of Silvio in Leoncavallo's Pagliacci at the Royal Theatre (Det Kongelige Teater). Melchior sang mostly minor baritone and bass roles for the Royal Danish Opera and provincial Scandianavian opera companies for the next few years.

In 1917 and 1918, Melchior studied to become a heldentenor, and made his tenor debut as Tannhäuser at Copenhagen's Royal Theatre in 1918.

In 1920, Melchior went to England. That year, he sang in an experimental radio broadcast to the Scandinavian capital cities from the Marconi Station in Chelmsford, England. Beginning in 1920, Melchior was also a frequent performer in London at Sir Henry Joseph Wood's Promenade Concerts in Queens Hall.

After further vocal studies in London and Munich, Melchior made his debuts as Siegmund and Parsifal at the first postwar Royal Opera House, Covent Garden Wagner performances and at the first postwar Bayreuth Festival. During the rest of the 1920's, Melchior debuted in all of his other most important roles, including the title roles in Siegfried (opera), Lohengrin (opera), Tristan und Isolde, and as Giuseppe Verdi's Otello.

Although Melchior sang at most of the theatres and concert halls of the Western world during his long career, he is best remembered as a member of the Metropolitan Opera company, where he sang 519 performances of his Wagnerian roles between 1926 and 1950.

Some of Melchior's most notable colleagues in the opera houses of the world included the sopranos Kirsten Flagstad, Lotte Lehmann, Helen Traubel, Marjorie Lawrence, Elisabeth Rethberg, the baritone Lawrence Tibbett and the conductors Bruno Walter, Wilhelm Furtwängler, Fritz Reiner, Thomas Beecham, Arturo Toscanini, Erich Leinsdorf, George Szell, and Otto Klemperer.

Between 1944 and 1952, Melchior performed in 5 Hollywood musicals for Metro-Goldwyn-Meyer and Paramount Pictures. In 1947, he put his hand and footprints in cement in the forecourt of Grauman's Chinese Theatre.

Following his unofficial retirement in 1955, Melchior made sporadic singing appearances. In the late 1960s, he set up a fund through Juilliard for the training of potential heldentenors called "The Lauritz Melchior Heldentenor Foundation."

An American citizen since 1947, Melchior died in Santa Monica, California in 1973. He is buried in the famous Assistens Kirkegaard cemetery in Copenhagen.