Carl Czerny (/ˈtʃɛərni/; German: [ˈtʃɛʁniː]; 21 February 1791 – 15 July 1857) was an Austrian composer, teacher, and pianist of Czech origin whose music spanned the late Classical and early Romantic eras. His vast musical production amounted to over a thousand works and his books of studies for the piano are still widely used in piano teaching. He was one of Ludwig van Beethoven's best-known pupils and would later on be one of the main teachers of Franz Liszt.

Carl Czerny was born in Vienna (Leopoldstadt) and was baptized in St. Leopold parish. His father was of Czech origin; his mother was Moravian. Czerny came from a musical family: his grandfather was a violinist at Nimburg, near Prague, and his father, Wenzel, was an oboist, organist and pianist. When Czerny was six months old, his father took a job as a piano teacher at a Polish manor and the family moved to Poland, where they lived until the third partition of Poland prompted the family to return to Vienna in 1795.

As a child prodigy, Czerny began playing piano at age three and composing at age seven. His first piano teacher was his father, who taught him mainly Bach, Haydn and Mozart. He began performing piano recitals in his parents' home. Czerny made his first public performance in 1800 playing Mozart's Piano Concerto No. 24 in C minor.

In 1801, Wenzel Krumpholz, a Czech composer and violinist, scheduled a presentation for Czerny at the home of Ludwig van Beethoven. Beethoven asked Czerny to play his Pathétique Sonata and Adelaide. Beethoven was impressed with the 10-year-old and accepted him as a pupil. Czerny remained under Beethoven's tutelage until 1804 and sporadically thereafter he transferred to be Johann Nepomuk Hummel’s star pupil. He particularly admired Beethoven's facility at improvisation, his expertise at fingering, the rapidity of his scales and trills, and his restrained demeanour while performing.

Czerny's autobiography and letters give many important references and details of Beethoven during this period. Czerny was the first to report symptoms of Beethoven's deafness, several years before the matter became public. Of his first meeting with Beethoven, he wrote: "I also noticed with that visual quickness peculiar to children that he had cotton which seemed to have been steeped in a yellowish ointment, in his ears."

Beethoven selected Czerny as pianist for the premiere of the former's Piano Concerto No. 1 in 1806 and, at the age of 21, in February 1812, Czerny gave the Vienna premiere of Beethoven's "Emperor" Piano Concerto. Czerny wrote that his musical memory enabled him to play virtually all of Beethoven's piano works by heart without exception and, during the years 1804–1805, he used to play these works in this manner at Prince Lichnowsky's palace once or twice a week, with the Prince calling out only the desired opus numbers. Czerny maintained a friendship with Beethoven throughout his life, and also gave piano lessons to Beethoven's nephew Carl.

At the age of fifteen, Czerny began a very successful teaching career. Basing his method on the teaching of Beethoven, Muzio Clementi and Johann Nepomuk Hummel, Czerny taught up to twelve lessons a day in the homes of Viennese nobility. His 'star' pupils included Theodor Döhler, Stephen Heller, Anna Sick, and Ninette de Belleville. In 1819, the father of Franz Liszt brought his son to Czerny, who recalled:

He was a pale, sickly-looking child, who, while playing, swayed about on the stool as if drunk...His playing was... irregular, untidy, confused, and...he threw his fingers quite arbitrarily all over the keyboard. But that notwithstanding, I was astonished at the talent Nature had bestowed upon him.