Did Antonio Salieri murder Wolfgang Mozart?

Nobody really knows for sure. Although the most accepted cause of Mozart's untimely death that he died of what is presumed to have been mercury poisoning while being treated for syphilis.

However, Salieri was accused of attempted murder by Mozart while he was still alive:

Allegations by Mozart

In Vienna in the 1790s, Mozart accused Salieri of plagiarism and of attempting to murder him with poison. As Mozart's music became more popular over the decades and Salieri's music was forgotten, Mozart's unsubstantiated allegations gained credence and tarnished Salieri's reputation.

The biographer Alexander Wheelock Thayer believes that Mozart's suspicions of Salieri could have originated with an incident in 1781 when Mozart applied to be the music teacher of the Princess of Württemberg, and Salieri was selected instead, and the following year Mozart was not selected to be the Princess's piano teacher either.

Later on, when Mozart's Le Nozze di Figaro was not liked by either the Emperor Joseph II nor by the public, Mozart blamed Salieri for the failure. "Salieri and his tribe will move heaven and earth to put it [Figaro] down," wrote Leopold Mozart. But at the time of the premiere of Figaro, Salieri was busy in France with his own operas. Thayer believes that the intrigues surrounding the failure of Figaro were instigated by the poet Abbate Casti against the Court Poet, Da Ponte, who wrote the Figaro libretto.

Later on, when Da Ponte was in Prague preparing the production of Mozart's setting of his Don Giovanni, the poet was ordered back to Vienna for a royal wedding for which Salieri's Axur would be performed. Obviously, Mozart was not pleased by this.

And yet Salieri did not intend to hinder Mozart's career. When Salieri was appointed Kapellmeister in 1788, instead of bringing out an opera of his own, he revived Figaro.

When in his later years, Salieri's health declined and he was hospitalized, there were rumors that Salieri confessed to Mozart's murder. Salieri's two nurses attested that Salieri said no such thing and that at least one of the two of them was with Salieri during his hospital stay.

After Salieri's death, the opera by Nicolai Rimsky-Korsakov, Mozart et Salieri (1898) started a tradition of dramatic license crossing into slander based on Mozart's allegations, continued by the play by Peter Shaffer, Amadeus (1979; and the Oscar winning original film based on the play, released in 1984, and "Director's Cut" was released on 2001 with an additional 20 minutes of footage).

In addition to the false allegations of murder, the movie also hurts Salieri's reputation by falsely portraying him as a mediocre composer and as a blasphemer burning a crucifix. His talent is patent throughout his works, and his religious devotion is undisputed by his biographers.