Toscanini was born in Parma, Emilia – Romagna, and won a scholarship to the local music conservatory, where he studied the cello. He joined the orchestra of an opera company, with which he toured South America in 1886. While presenting Aida in Rio de Janeiro, Leopoldo Miguez, the locally hired conductor, reached the summit of a two - month escalating conflict with the performers due to his rather poor command of the work, to the point that the singers went on strike and forced the company's impresario to seek a substitute conductor. But on the evening of June 30, 1886 maestro Carlo Superti found himself booed by the audience, now prompted by the disgruntled Miguez. Yet another last minute substitute conductor, Aristide Venturi, could not overcome a hostile, hollering public, and was forced to leave the podium. In desperation, the singers suggested the name of their assistant Chorus Master, who knew the whole opera by heart. Although he had no conducting experience, Toscanini was forcibly persuaded by the musicians to take up the baton at 9:15 P.M., discarded the score, and led a sensational performance of the two - and - a - half hour opera completely from memory. The public was taken by surprise, at first by the youth and sheer aplomb of this unknown conductor, then by his solid mastery. The result was astounding acclaim. For the rest of that season Toscanini conducted eighteen operas, all with absolute success. Thus began his career as a conductor, at age 19.

Upon returning to Italy, Toscanini set out on a dual path for some time. He continued to conduct, his first appearance in Italy being at the Teatro Carignano in Turin, on November 4, 1886, in the world premiere of the revised version of Alfredo Catalani's Edmea (it had had its premiere in its original form at La Scala, Milan, on 27 February of that year). This was the beginning of Toscanini's life long friendship and championing of Catalani; he even named his first daughter Wally after the heroine of Catalani's opera La Wally. However, he also returned to his chair in the cello section, and participated as cellist in the world premiere of Verdi's Otello (La Scala, Milan, 1887) under the composer's supervision. Verdi, who habitually complained that conductors never seemed interested in directing his scores the way he had written them, was impressed by reports from Arrigo Boito about Toscanini's ability to interpret his scores. The composer was also impressed when Toscanini consulted him personally about the Te Deum, suggesting an allargando where it was not set out in the score. Verdi said that he had left it out for fear that "certain interpreters would have exaggerated the marking".

Gradually the young musician's reputation as an operatic conductor of unusual authority and skill supplanted his cello career. In the following decade he consolidated his career in Italy, entrusted with the world premieres of Puccini's La bohème and Leoncavallo's Pagliacci. In 1896, Toscanini conducted his first symphonic concert (in Turin, with works by Schubert, Brahms, Tchaikovsky, and Wagner). He exhibited a considerable capacity for hard work: in 1898 he conducted 43 concerts in Turin. By 1898 he was principal conductor at La Scala, where he remained until 1908, returning as Music Director, 1921 - 1929. He took the Scala Orchestra to the United States on a concert tour in 1920/21; it was during that tour that Toscanini made his first recordings (for the Victor Talking Machine Company).

Outside of Europe, he conducted at the Metropolitan Opera in New York (1908 – 1915) as well as the New York Philharmonic Orchestra (1926 – 1936). He toured Europe with the New York Philharmonic in 1930; he and the musicians were acclaimed by critics and audiences wherever they went. Toscanini was the first non-German conductor to appear at Bayreuth (1930 – 1931), and the New York Philharmonic was the first non-German orchestra to play there. In the 1930s he conducted at the Salzburg Festival (1934 – 1937) and at the inaugural concert in 1936 of the Palestine Orchestra (later renamed the Israel Philharmonic Orchestra) in Tel Aviv, and later performed with them in Jerusalem, Haifa, Cairo and Alexandria.

During his career, Toscanini worked with such legendary artists as Enrico Caruso, Feodor Chaliapin, Ezio Pinza, Jussi Bjoerling, and Geraldine Farrar. Although he also worked with Wagnerian heldentenor Lauritz Melchior, he would not work with Melchior's frequent partner Kirsten Flagstad after her political sympathies became suspect during World War II; it was Helen Traubel who sang with Melchior instead of Flagstad at the Toscanini concerts.

In 1919, Toscanini ran unsuccessfully as a Fascist parliamentary candidate in Milan. He had been called "the greatest conductor in the world" by Fascist leader Benito Mussolini. However, he became disillusioned with fascism and repeatedly defied the Italian dictator after the latter's ascent to power in 1922. He refused to display Mussolini's photograph or conduct the Fascist anthem Giovinezza at La Scala. He raged to a friend, "If I were capable of killing a man, I would kill Mussolini."

At a memorial concert for Italian composer Giuseppe Martucci on May 14, 1931 at the Teatro Comunale in Bologna, he was ordered to begin by playing Giovinezza but he refused even though the fascist foreign minister Galeazzo Ciano was present in the audience. Afterwards he was, in his own words, "attacked, injured and repeatedly hit in the face" by a group of blackshirts. Mussolini, incensed by the conductor's refusal, had his phone tapped, placed him under constant surveillance and took away his passport. The passport was returned only after world outcry over Toscanini's treatment. He left Italy in 1939 and did not return until 1946, when he returned to conduct a concert at the restored La Scala Opera House, which had been bombed during World War II.

Fleeing Italy, he returned to the United States where the NBC Symphony Orchestra was created for him in 1937. He conducted his first NBC broadcast concert on December 25, 1937, in NBC Studio 8-H in New York City's Rockefeller Center. The acoustics of the specially built studio were very dry; some remodeling in 1939 added a bit more reverberation. (In 1950, the studio was further remodeled for television productions; today it is used by NBC for Saturday Night Live. In 1980, it was used by Zubin Mehta and the New York Philharmonic Orchestra in a series of special televised NBC concerts called "Live From Studio 8H", the first one being a tribute to Toscanini, punctuated by clips from his television concerts.)

The NBC broadcasts were preserved on large transcription discs, recorded at both 78 rpm and 33 1/3 rpm, until NBC began using magnetic tape in 1947. NBC used special RCA high fidelity microphones both for the broadcasts and for recording them; these microphones can be seen in some photographs of Toscanini and the orchestra. Some of Toscanini's recording sessions for RCA Victor were mastered on sound film in a process developed about 1941, as detailed by RCA producer Charles O'Connell in his memoirs, On and Off The Record. In addition, hundreds of hours of Toscanini's rehearsals with the NBC were preserved and are now housed in the Toscanini Legacy archive at The New York Public Library.

Toscanini was often criticized for neglecting American music; however, on November 5, 1938, he conducted the world premieres of two orchestral works by Samuel Barber, Adagio for Strings and Essay for Orchestra. In 1945, he led the orchestra in recording sessions of the Grand Canyon Suite by Ferde Grofé in Carnegie Hall (supervised by Grofé) and An American in Paris by George Gershwin in NBC's Studio 8-H. He also conducted broadcast performances of Copland's El Salon Mexico; Gershwin's Rhapsody in Blue with soloists Earl Wild and Benny Goodman and Piano Concerto in F with pianist Oscar Levant; and music by other American composers, including marches of John Philip Sousa. He even wrote his own orchestral arrangement of The Star Spangled Banner, which was incorporated into the NBC Symphony's performances of Verdi's Hymn of the Nations. (Earlier, while music director of the New York Philharmonic, he conducted music by Abram Chasins, Bernard Wagenaar, and Howard Hanson.)

In 1940, Toscanini took the orchestra on a "goodwill" tour of South America. Later that year, Toscanini had a disagreement with NBC management over their use of his musicians in other NBC broadcasts. This, among other reasons, resulted in a letter which Toscanini wrote on 10 March 1941 to RCA's David Sarnoff. He stated that he now wished "to withdraw from the militant scene of Art" and thus declined to sign a new contract for the up-coming winter season, but left the door open for an eventual return "if my state of mind, health and rest will be improved enough". So Leopold Stokowski was engaged on a three year contract instead and served as the NBC Symphony's music director from 1941 until 1944. Toscanini's state of mind soon underwent a change and he returned as Stokowski's co-conductor for the latter's second and third seasons resuming full control in 1944.

One of the more remarkable broadcasts was in July 1942, when Toscanini conducted the American premiere of Dmitri Shostakovich's Symphony No. 7. Due to World War II, the score was microfilmed in the Soviet Union and brought by courier to the United States. Stokowski had previously given the US premieres of Shostakovich's 1st, 3rd and 6th Symphonies in Philadelphia, and in December 1941 urged NBC to obtain the score of the 7th as he wanted to conduct its premiere as well. But Toscanini coveted this for himself and there were a number of remarkable letters between the two conductors (reproduced by Harvey Sachs in his biography) before Stokowski agreed to let Toscanini have the privilege of conducting the first performance. Unfortunately for New York listeners, a major thunderstorm virtually obliterated the NBC radio signals there, but the performance was heard elsewhere and preserved on transcription discs. It was later issued by RCA Victor in the 1967 centennial boxed set tribute to Toscanini, which included a number of NBC broadcasts never released on discs. In Testimony Shostakovich himself expressed a dislike for the performance, after he heard a recording of the broadcast. In Toscanini's later years the conductor expressed dislike for the work and amazement that he had actually conducted it.

In the summer of 1950, Toscanini led the orchestra on an extensive transcontinental tour. It was during that tour that the well known photograph of Toscanini riding the ski lift at Sun Valley, Idaho, was taken. Toscanini and the musicians traveled on a special train chartered by NBC.

The NBC concerts continued in Studio 8-H until the fall of 1950. They were then held in Carnegie Hall, where many of the orchestra's recording sessions had been held, due to the dry acoustics of Studio 8-H. The final broadcast performance, an all-Wagner program, took place on April 4, 1954, in Carnegie Hall. During this concert Toscanini suffered a memory lapse reportedly caused by a transient ischemic attack, although some have attributed the lapse to having been secretly informed that NBC intended to end the broadcasts and disband the NBC orchestra. He never conducted live in public again. That June, he participated in his final recording sessions, remaking portions of two Verdi operas so they could be commercially released. Toscanini was 87 years old when he retired. After his retirement, the NBC Symphony was reorganized as the Symphony of the Air, making regular performances and recordings, until it was disbanded in 1963.

On radio, he conducted seven complete operas, including La bohème, La traviata, and Otello, all of which were eventually released on records and CD, thus enabling the modern listening public to have at least some idea of what an opera conducted by Toscanini sounded like.

With the help of his son Walter, Toscanini spent his remaining years editing tapes and transcriptions of his performances with the NBC Symphony. The "approved" recordings were issued by RCA Victor, which also has issued his recordings with the La Scala Orchestra, the New York Philharmonic Orchestra, and the Philadelphia Orchestra. His recordings with the BBC Symphony Orchestra (1937 – 39) and the Philharmonia Orchestra (1952) were issued by EMI. Various companies have issued recordings on compact discs of a number of broadcasts and concerts that he did not officially approve. Among these are stereophonic recordings of his last two NBC broadcast concerts.

Sachs and other biographers have documented the numerous conductors, singers, and musicians who visited Toscanini during his retirement. He was a big fan of early television, especially boxing and wrestling telecasts, as well as comedy programs.

Toscanini died at age 89 of a stroke at his home in the Riverdale section of the Bronx in New York City on January 16, 1957. His body was returned to Italy and was interred in the Cimitero Monumentale in Milan. His epitaph is taken from one account of his remarks concluding the 1926 premiere of Puccini's unfinished Turandot: "Qui finisce l'opera, perché a questo punto il maestro è morto" ("Here the opera ends, because at this point the maestro died"). During his funeral service, Leyla Gencer sang an aria from Verdi's Requiem.

In his will, he left his baton to his protégée Herva Nelli, who sang the title role in Toscanini's performance of Aida as well as Desdemona in Otello.

Toscanini was posthumously awarded the Grammy Lifetime Achievement Award in 1987.

Toscanini married Carla De Martini on June 21, 1897, when she was not yet 20 years old. Their first child, Walter, was born on March 19, 1898. A daughter, Wally, was born on January 16, 1900. Carla gave birth to another boy, Giorgio, in September 1901, but he died of diphtheria on June 10, 1906. Then, that same year, Carla gave birth to their second daughter, Wanda. Toscanini worked with many great singers and musicians throughout his career, but few impressed him as much as the Russian - American pianist Vladimir Horowitz. They worked together a number of times and even recorded Brahms' second piano concerto and Tchaikovsky's first piano concerto with the NBC Symphony for RCA. Horowitz also became close to Toscanini and his family. In 1933, Wanda Toscanini married Horowitz, with the conductor's blessings and warnings. It was Wanda's daughter, Sonia, who was once photographed by Life playing with the conductor. During World War II, Toscanini lived in Wave Hill, a historic home in Riverdale. Despite the reported infidelities revealed in Toscanini's letters documented by Harvey Sachs, he remained married to Carla until she died on June 23, 1951.

At La Scala, which had what was then the most modern stage lighting system installed in 1901 and an orchestral pit installed in 1907, Toscanini pushed through reforms in the performance of opera. He insisted on dimming the house lights during performances. As his biographer Harvey Sachs wrote: "He believed that a performance could not be artistically successful unless unity of intention was first established among all the components: singers, orchestra, chorus, staging, sets, and costumes."

Toscanini favored the traditional orchestral seating plan with the first violins and cellos on the left, the violas on the near right, and the second violins on the far right.

Toscanini conducted the world premieres of many operas, four of which have become part of the standard operatic repertoire: Pagliacci, La bohème, La fanciulla del West and Turandot; he took an active role in Alfano's completion of Puccini's Turandot. He also conducted the first Italian performances of Siegfried, Götterdämmerung, Salome, Pelléas et Mélisande, and Euryanthe, as well as the South American premieres of Tristan und Isolde and Madama Butterfly and the North American premiere of Boris Godunov. He also conducted the world premiere of Samuel Barber's most famous work, the Adagio for Strings.