Eugène Ysaÿe (July 16, 1858 – May 12, 1931) was a Belgian violinist and composer.

He was born in Liège, Belgium, and began violin lessons at the age of four with his father, and later studied with Joseph Massart, Henryk Wieniawski, and Henri Vieuxtemps.

After his graduation, Ysaÿe was the principal violin of the Benjamin Bilse beer-hall orchestra, which later developed into the Berlin Philharmonic. Many musicians of note and influence came regularly to hear this orchestra and Ysaÿe in particular, among whom figured Joseph Joachim, Franz Liszt, Clara Schumann, and Anton Rubinstein, who asked that Ysaÿe be released from his contract to accompany him on tour.

When Ysaÿe was twenty-seven years old, he was recommended as a soloist for one of the Concerts Colonne in Paris, which was the start of his great success as a concert artist. The next year, Ysaÿe received a professorship at the Brussels Conservatoire in his native Belgium. This began his career as a teacher, which was to remain one of his main occupations after leaving the conservatory in 1898 and into even his last years. Among his more respected pupils are Josef Gingold, the violist William Primrose, Louis Persinger, Alberto Bachmann, and Mathieu Crickboom.

During his tenure as professor at the Conservatoire, Ysaÿe continued to tour an ever-broadening section of the world, including all of Europe, Russia, and the United States. Despite health concerns, particularly regarding the (probably diabetes-related) condition of his hands, Ysaÿe was at his best when performing, and many prominent composers dedicated major works to him, including Claude Debussy, Camille Saint-Saëns, César Franck, and Ernest Chausson.

As his physical ailments grew more prohibitive, Ysaÿe turned more and more to teaching and an early love, composition. Among his most famous works are six unaccompanied violin sonatas, Op.27, a quartet, Harmonies du Soir, Op.31, and an opera, Peter the Miner, written at the end of his life in the Walloon dialect.

As a performer, Ysaÿe was compelling and highly original. Pablo Casals claimed never to have heard a violinist play in tune before Ysaÿe , and Carl Flesch called him 'the most outstanding and individual violinist I have ever heard in my life'.

Ysaÿe was the possessor of a large and flexible tone, influenced by a varied and nearly continuous vibrato. While he, like many of his contemporaries, used the portamento more often than modern players, he used it with discretion and taste and never as a mere technical aid.

Possibly the most distinctive feature of Ysaÿe's interpretations was his masterful rubato. Rubato is literally 'stealing' of time; it usually implies a mere flexing of tempo for expressive purposes. Ysaÿe's rubato is something apart; whenever he stole time from one note, he paid it back in another place, allowing his accompanist to maintain strict tempo under his free cantilena. This kind of rubato fits the description of Frederic Chopin's rubato, but, of all the early performers on record, is the only real display of it.

Ysaÿe was an artist who was not equally at home in all repertoire; though admired for his Bach and Beethoven interpretations, he was in his best form in the works of more modern composers, the late Romantics and early modern writers. Particularly Max Bruch, Camille Saint-Saëns, and Franck called him their greatest interpreter, and in those and similar composers' works he was unquestionedly supreme. His technique was brilliant and finely honed, but never employed without some musical purpose in mind. In this respect he could be considered the first of the modern type of violinist, whose technique is without the gaps of some earlier artists, but not used for its own sake so much as in the service of the music at hand.

On his passing in 1931, Eugène Ysaÿe was interred in the Ixelles Cemetery in Brussels.da:Eugene Ysaÿe de:Eugène Ysaye fr:Eugène Ysaÿe it:Eugène Ysaÿe ja:ウジェーヌ・イザイ nl:Eugène Ysaÿe