During the course of his lifetime, Ludwig van Beethoven (1770–1827) established relationships with many of his musical contemporaries. Beethoven was notoriously temperamental, eccentric and difficult to get along with; the history of his many relationships is replete with arguments, misunderstandings, and reconciliations. Beethoven had well-known quarrels with his one-time teachers, Joseph Haydn and Antonio Salieri, with the piano virtuoso and composer Johann Nepomuk Hummel, and the German composer Carl Maria von Weber. Conversely, he regarded Franz Schubert positively, praising the latter's compositions.

Luigi Cherubini

Beethoven met the composer Luigi Cherubini on the latter's journey to Vienna in 1805. Cherubini, a longtime resident of Paris, was invited to mount a production of his opera Die Tage der Gefahr (or Der Wasserträger) after the success of his 1791 opera Lodoïska, which was staged by Emanuel Schikaneder on 23 March 1803 at the Theater an der Wien. Cherubini's time in Vienna was generally unhappy, but he did have the opportunity to meet Beethoven. Cherubini was in attendance for the first performances of Beethoven's opera Fidelio, to which he reacted sneeringly. He also described Beethoven's piano style as "rough", and more famously the man himself as "an unlicked bear cub". Despite this, Beethoven named Cherubini as the greatest contemporary composer other than himself.

Johann Wolfgang von Goethe

Beethoven had already read and admired Johann Wolfgang von Goethe's works during his youth in Bonn, long before their first meeting in 1812. His first Goethe settings were produced around 1790. Beethoven announced his music to Egmont in a letter to the poet in the spring of 1811 with the following words: "I am only able to approach you with the greatest veneration [and] with an inexpressibly deep feeling for your glorious creations." He had already set 18 texts by Goethe, and two others were to follow. Goethe therefore occupies a privileged position in Beethoven's vocal works. Beethoven met Goethe at Teplitz in 1812, and a possibly apocryphal story by Bettina von Arnim described Beethoven refusing to bow to visiting royalty, much to Goethe's consternation.

Joseph Haydn

Perhaps the most important relationship in Beethoven's early life, and certainly the most famous, was the young pianist's tutorship under the Austrian composer Joseph Haydn. Beethoven studied with a number of composers and teachers in the period 1792–95, including Antonio Salieri and Johann Georg Albrechtsberger. However, of all Beethoven's teachers, Haydn enjoyed the greatest reputation, having just returned from his first successful voyage to London. Possibly as early as his first trip to London in 1790, Haydn agreed to take on Beethoven as a student.

There is evidence that Haydn assigned his student composition exercises based on the Fux text Gradus ad Parnassum. During the course of the year, however, the relationship between the two men soured. According to contemporary accounts, the issue surfaced most notably upon the publication of Beethoven's first compositions, the Op. 1 piano trios. Wishing to assist the young composer, Haydn suggested that Beethoven include the phrase "pupil of Haydn" underneath his name in order to garner advantage from Haydn's considerable fame. There is generally strong evidence of Haydn's goodwill toward Beethoven, including an interest in taking his pupil with him on his second London voyage, and the personal missives Haydn sent to Beethoven's early patron, Maximilian Francis of Austria, Elector of Cologne.

Beethoven, however, seems to have harbored ill-will toward Haydn during various points of his life. At the suggestion that he include the phrase "pupil of Haydn", Beethoven bristled. According to the account left by Ferdinand Ries, "Beethoven was unwilling to, because, as he said, although he had some instruction from Haydn, he had never learned anything from him." The bad feelings produced by the Op. 1 Trios were compounded upon their first performance. Haydn, present in the audience, is reported to have recommended against the publication of the C minor Trio (Op. 1, No. 3) since he suspected the music would not gain public acceptance. Beethoven considered the C minor the best of the trios and interpreted Haydn's advice as an indication of his envy.

Despite this, however, Beethoven and Haydn remained on relatively good terms until Haydn's death in 1809. Beethoven attended the concert in honor of Haydn's 76th birthday, and it is said that he "knelt down before Haydn and fervently kissed the hands and forehead of his old teacher".

Haydn's towering reputation in Vienna made it hard for Beethoven to be openly antagonistic. However, Haydn was also genuinely admiring of Beethoven's compositions, a trait that usually succeeded in earning Beethoven's goodwill.

In his renowned biography of Beethoven, Maynard Solomon notes that, in his later years, "Beethoven unfailingly referred to his old master in terms of reverence, regarding him as the equal" of Mozart and Bach.

Johann Nepomuk Hummel

Johann Nepomuk Hummel, born in 1778, was a fixture in the Viennese musical world. A child prodigy and former pupil of Mozart, Hummel was renowned for his incredible virtuosity at the keyboard and legendary prowess at improvisation. Alongside Beethoven, he was widely considered the finest performer of his day. For many years, Hummel enjoyed a close friendship with Beethoven.

Several incidents, however, marred their relationship. In one famous incident, Beethoven was invited by Prince Nikolaus II Esterhazy to write a mass for his wife in 1807. Beethoven agreed and produced the Mass in C, which was performed at the prince's estate in Eisenstadt. Hummel was at the time the Kapellmeister, having been appointed Haydn's successor to the Esterhazy court. The performance did not go well, and the prince is purported to have made a barbed remark to Beethoven afterwards. According to Schindler, Hummel laughed at the prince's words, compounding the always-sensitive Beethoven's feelings of humiliation and persecution. Beethoven promptly left Eisenstadt and carried the grudge for years afterward. This incident, however, likely did not prompt the eventual falling-out between the two men.

A more likely source of contention between them was artistic. Hummel was well known for his keyboard arrangements of Beethoven's works, particularly his symphonies. Beethoven disliked Hummel's style of performance and composition, and, according to Ignaz Moscheles, objected to Hummel's arrangements. Some time in the late 1810s, disagreement surfaced, the exact cause of which is unknown, but which may well have centered on discord over Hummel's arrangements of Beethoven's music.

Hummel spent most of the 1820s at the Weimar Court, where he was a friend of Johann Wolfgang von Goethe, and did not see Beethoven again until a remarkable reconciliation took place between the two men at Beethoven's deathbed. Hummel, hearing of Beethoven's serious illness, travelled from Weimar to Vienna to visit his erstwhile friend. According to the account left by Hummel's then-student Ferdinand Hiller, who accompanied his teacher, Hummel may have been motivated by more than compassion. Hummel solicited Beethoven's signature upon a petition he was taking to the Bundestag in order to protect his compositions (and those of others) from illegal copying. All told, Hummel visited Beethoven three times while he was on his deathbed, the last being on 23 March 1827, just three days before his death, and was present at his funeral.

Franz Liszt

On 13 April 1823, the eleven-year-old Hungarian pianist Franz Liszt (1811–1886) performed in Vienna. It was said that the 53-year-old Beethoven gave him a kiss – the so-called Weihekuss, or 'kiss of consecration' – for his marvellous playing. This is unlikely to be true, as Beethoven was profoundly deaf by this time. A more reasonable account of the Beethoven kiss event is reported in the reminiscences of the pianist Ilka Horovitz-Barnay:

"The most memorable time I experienced with Liszt was when he told me of his meeting with Beethoven. 'I was about eleven years old', he began, 'when my highly esteemed teacher Czerny introduced me to Beethoven. He had long before told him about me and had asked him to hear me play. But Beethoven had aversions against prodigies and for a long time refused to hear me. Finally though he was persuaded by my indefatigable teacher Czerny and said: "Then for God's sake – bring the little rascal".

"'It was one morning about ten o'clock when we entered the two small rooms of the Schwarzspanierhaus, where Beethoven lived. I was somewhat embarrassed – but Czerny kindly encouraged me. Beethoven was sitting by the window at a long narrow table working. For a moment he looked at us with a serious face, said a couple of quick words to Czerny but turned silent as my dear teacher signaled to me to go to the piano.

"'First I played a small piece of Ries [Ferdinand Ries, another pupil of Beethoven]. When I had finished Beethoven asked if I could play a fugue by Bach. I chose the C minor fugue from The Well-Tempered Clavier. "Can you transpose this fugue?" Beethoven asked.

"'Fortunately I could. After the finishing chord I looked up. Beethoven's deep glowing eyes rested upon me – but suddenly a light smile flew over his otherwise serious face. He approached me and stroked me several times over my head with affection.

"'"Well – I'll be blowed" he whispered, "such a little devil".

"'Suddenly my courage rose: "May I play one of your pieces?" I asked with audacity. Beethoven nodded with a smile. I played the first movement of his C major piano concerto [No. 1]. When I had finished Beethoven stretched out his arms, kissed me on my forehead and said in a soft voice:

"'"You go on ahead. You are one of the lucky ones! It will be your destiny to bring joy and delight to many people and that is the greatest happiness one can achieve"'.

"Liszt told me this with great emotion; his voice trembled but you could feel what divine joy these simple words had given him. Never did Liszt – the human being – make a greater impression on me. The flamboyant man-of-the-world, the revered artist was gone; this great moment he had experienced in his childhood still resounded in his soul. For a little while he was silent – then he said quietly:

"'This was the proudest moment in my life – the inauguration to my life as artist. I tell this very rarely – and only to special friends.'"

This story is somewhat more convincing, although Beethoven was just as deaf in 1822 as in 1823. It is certainly possible that Beethoven was able to appraise Liszt's playing by observing his fingerings and feeling the vibrations of the piano with his hand. However, at the time the meeting supposedly occurred, Beethoven was not residing in the Schwarzspanierhaus; he didn't move there until late 1825. But when Liszt told this story, he was in his latter years, and his memory may have been a little faulty, if the story itself was not a confabulation.

Wolfgang Amadeus Mozart

Wolfgang Amadeus Mozart (1756–1791) was already an accomplished and renowned composer in Vienna when the then 16-year-old Beethoven first visited the city in 1787. The two may have met during Beethoven's six-month stay there, although there are no contemporary documents that provide any evidence for this. According to secondary accounts given by writer Otto Jahn, Beethoven was taken to meet Mozart and played for him. Beethoven may also have received lessons from Mozart.