Jakob Ludwig Felix Mendelssohn Bartholdy (3 February 1809 – 4 November 1847), widely known as Felix Mendelssohn, was a German composer, pianist, organist and conductor of the early Romantic period. Mendelssohn's compositions include symphonies, concertos, piano music, organ music and chamber music. His best-known works include the overture and incidental music for A Midsummer Night's Dream (which includes his "Wedding March"), the Italian and Scottish Symphonies, the oratorios St. Paul and Elijah, the Hebrides Overture, the mature Violin Concerto, the String Octet, and the melody used in the Christmas carol "Hark! The Herald Angels Sing". Mendelssohn's Songs Without Words are his most famous solo piano compositions.

Mendelssohn's grandfather was the Jewish philosopher Moses Mendelssohn, but Felix was initially raised without religion until he was baptised aged seven into the Reformed Christian church. He was recognised early as a musical prodigy, but his parents were cautious and did not seek to capitalise on his talent. His sister Fanny Mendelssohn received a similar musical education and was a talented composer and pianist in her own right; some of her early songs were published under her brother's name and her Easter Sonata was for a time mistakenly attributed to him after being lost and rediscovered in the 1970s.

Mendelssohn enjoyed early success in Germany, and revived interest in the music of Johann Sebastian Bach, notably with his performance of the St Matthew Passion in 1829. He became well received in his travels throughout Europe as a composer, conductor and soloist; his ten visits to Britain – during which many of his major works were premiered – form an important part of his adult career. His essentially conservative musical tastes set him apart from more adventurous musical contemporaries, such as Franz Liszt, Richard Wagner, Charles-Valentin Alkan and Hector Berlioz. The Leipzig Conservatory, which he founded, became a bastion of this anti-radical outlook.

After a long period of relative denigration due to changing musical tastes and antisemitism in the late 19th and early 20th centuries, his creative originality has been re-evaluated. He is now among the most popular composers of the Romantic era.