Sometimes described as the most recorded singer in history, Fischer-Dieskau died in the town of Berg on Starnberg Lake in Bavaria, the Bavarian State Opera announced on its website.
"The death of Dietrich Fischer-Dieskau is a great loss for the entire music world. Through his interpretations of vocals he decisively influenced the art of opera singing. Today's vocals would be unthinkable without the influence of Dietrich Fischer-Dieskau," the opera's administrator, Nikolaus Bachler, said in a statement.
The late soprano Elizabeth Schwarzkopf called him "a born god who has it all" and he was in high demand from opera houses and for recitals during a career that spanned almost 50 years until his retirement in 1992.
Born in Berlin in 1925, Fischer-Dieskau was trained at the Berlin School of Music and presented his first recital and was engaged by the City Opera of Berlin in 1947.
He emerged to international prominence after the end of World War Two and was particularly noted for his interpretations of the German art song, or lieder, especially the high romantic works of Schubert such as the song cycles Winterreise and Die schoene Muellerin.
One of the highlights of his career was his appearance in 1962 at England's newly built Coventry Cathedral, at the invitation of Benjamin Britten for the world premiere of the composer's "War Requiem".
Britten wrote parts expressly for the German Fischer-Dieskau and the English tenor, Peter Pears, in a work that conveys the devastating impact of war.
Fischer-Dieskau was highly praised for his interpretations of Falstaff in Verdi's opera of the same name, for his performance as Count Almaviva in Mozart's "Marriage of Figaro" and for the hugely demanding role of Hans Sachs in Wagner's "Die Meistersinger von Nurnberg".
He teamed up with many of the best orchestras, conductors and accompanists of the age, including pianists Alfred Brendel, Gerald Moore and Daniel Barenboim and conductors Herbert von Karajan and Leonard Bernstein.
He had guest appearances at some of the world's most renowned opera houses, in Vienna, Munich and Hamburg as well as London's Covent Garden, New York's Carnegie Hall and the festivals of Bayreuth and Edinburgh.
The New York Times once called him "the world's best singer" and colleagues and music lovers sang his praises.
"He had only to sing one phrase," Moore, his frequent accompanist, wrote in his memoirs, "before I knew I was in the presence of a master."
In 1992 he gave a farewell concert in the National Theater in Munich and afterwards worked as a director, author and taught master classes.
He is survived by his wife, the Hungarian-born soprano Julia Varady.
