Johan Botha portrays Prince Calaf during a dress rehearsal of “Turandot” at the Met in 2004. (Hiroko Masuike/Associated Press)

Johan Botha, a South African tenor known to patrons of the world’s most prestigious opera houses for the unusual combination of dramatic force and lyrical grace that he brought to a seemingly boundless repertoire, died Sept. 8 in Vienna. He was 51.

Raphaela Hödl, a representative of the Michael Lewin artistic management firm, confirmed his death in an email, citing a “severe illness.” Mr. Botha was reportedly diagnosed with cancer in November 2015 and announced last month that he was “free” of the disease.

Mr. Botha spent much of his adult life in the Austrian capital, where he sang often at the Vienna State Opera, as well as at houses including Milan’s La Scala, London’s Royal Opera House at Covent Garden and the Metropolitan Opera in New York, where he sang 10 roles, in a total of 80 performances, since his debut there in 1997.

His success on the stage represented a private as well as professional triumph.

“As a child I was dyslexic,” he told Opera News. “Because of this, people thought I was stupid. I could not read words, and I couldn’t spell. What I could do was read music. This proved to everyone that I could accomplish something, and singing became my life.”

Trained initially as a bass-baritone, he possessed the heavy vocal power of a heldentenor, the type of voice suited for the dramatic roles of German opera. Yet he also was capable of the shining brilliance that distinguishes the best lyric tenors in the Italian tradition.

With his dual gifts, Mr. Botha excelled in the Wagnerian repertoire as the knight Walther of “Die Meistersinger von Nürnberg,” Siegmund in “Die Walküre” and the title character of “Tannhäuser,” which he sang at the Met last season.

In the Italian canon, he appeared as Canio in Leoncavallo’s “Pagliacci,” the role in which he made his Met debut; the title character of “Otello,” based on Shakespeare’s tragedy, and the Egyptian warrior Radames of “Aida,” both by Verdi; and Prince Calaf in Puccini’s “Turandot.”

Mr. Botha was the “rarest type of tenor voice,” F. Paul Driscoll, the editor in chief of Opera News, said in an interview.

If critics identified in Mr. Botha a weakness, it lay in his acting abilities, which some observers found lacking in comparison with his vocal power. Mr. Botha said he was wounded when critics remarked on his girth, which at times appeared incompatible with the romantic, even swashbuckling nature of the characters he portrayed.

He said he had done “every diet you can think of” and that he was “fighting a losing battle.”

“We have all been conditioned by television,” he told Opera News. “Everyone on television looks like a model, and now people expect opera singers to look the same. But believe me, no anorexic could sing Otello.”

He was, however, heartened by a comment from one colleague.

“You might not look like a lover,” he recalled her telling him, “but you sure sing and act like one.”

Mr. Botha was born in Rustenburg, 70 miles west of Pretoria, on Aug. 19, 1965. He discovered opera through his father, who listened to recordings of Enrico Caruso, Beniamino Gigli and Richard Tucker.

“When I was five, I already knew all those famous tenor arias,” Mr. Botha told Opera News. “Each time my father put on one of his records, I took great pleasure in joining in, with my squeaky falsetto voice, at the top of my lungs. Naturally, my father didn’t really like my trying to compete with those legendary singers, and he always shut me up.”

Mr. Botha recalled declaring to his father that “someday I’ll sing the way they do.”

His parents supported his musical ambitions, which he pursued first by singing in choirs. Later, he studied opera with a teacher who helped him compile a list of operatic roles to learn and opera houses where he wished to sing.

In 1989, Mr. Botha debuted in Roodepoort, South Africa, as Max in Weber’s “Der Freischütz.” He later sang in the chorus at the Wagner festival in Bayreuth, Germany, and honed his abilities while singing small roles in Europe. He was propelled to greater recognition in 1993 when, on two days’ notice, he took on the role of Pinkerton in Puccini’s “Madame Butterfly” at the Opera Bastille in Paris.

In addition to performing fully staged operas, Mr. Botha appeared in concerts with ensembles including the Vienna and Berlin philharmonics. His solo albums included “Italian Arias” (2001) and “Richard Wagner” (2004).

Survivors include his wife, Sonja, and two sons, Marius and Louis.

For Mr. Botha, opera’s significance transcended its musical beauty. He was particularly moved by the character of Canio in “Pagliacci.” Overcome by jealousy for his wife, the clown mixes theater and reality and stabs her during a performance by their acting troupe.

“I believe everybody can learn from opera,” Mr. Botha once told the Associated Press. “I’m a very religious person. I believe God has put this music into my hands so I can warn somebody who is at the performance and having problems. He will see how jealousy can end.”