The "Maple Leaf Rag" (copyright registered on September 18, 1899) is an early ragtime musical piece composed for piano by Scott Joplin. It was one of Joplin's early works, becoming the model for ragtime compositions by subsequent composers. It is one of the most famous of all ragtime pieces. Its success led to Joplin being dubbed the "King of Ragtime" by his contemporaries. The piece gave Joplin a steady, modest income for the rest of his life.

Despite ragtime's decline after Joplin's death in 1917, the "Maple Leaf Rag" continued to be recorded by many well-known artists. The ragtime revival of the 1970s brought it back to mainstream public notice once again.

The "Maple Leaf Rag" is associated with the city of Sedalia, Missouri, although there is no record of Joplin having a permanent residence there before 1904. Joplin arrived in Sedalia in 1894 as a touring musician and stayed with the family of Arthur Marshall, who later became one of Joplin's students and a ragtime composer in his own right. Joplin played as a solo musician at dances and at the major black clubs in Sedalia, among them the "Maple Leaf Club". It is possible that the rag was named after the Maple Leaf Club, although there is no direct evidence to prove the link, and there were probably many other possible sources for the name in and around Sedalia at the time.

Although there were hundreds of rags in print by the time of the "Maple Leaf Rag's" publication, Joplin was not far behind. His first published rag was "Original Rags" (March 1899). The "Maple Leaf Rag" was already known in Sedalia prior to its publication in 1899; composer and pianist Brun Campbell claimed to have seen the manuscript of the work in or around 1898. Prior to its publication, Joplin anticipated that the piece would be a success—he told Arthur Marshall that "The Maple Leaf will make me the king of ragtime composers".

The exact circumstances which led to publication of the "Maple Leaf Rag" are unknown, and there are versions of the event which contradict each other. After approaching several publishers, Joplin signed a contract with John Stillwell Stark on August 10, 1899 for a royalty of one cent ($0.39 in 2025) on all sales of the rag, with a minimum sales price of 25 cents($9.68 in 2025). The "Maple Leaf Rag" was published between August 10 and September 20, 1899, when the United States Copyright Office received two copies of the score. It was reissued in 1900 or 1901 with a new cover showing a green maple leaf and a photograph of Joplin. In 1903, Stark issued a "Maple Leaf Rag Song", an arrangement of Joplin's music with words by Sydney Brown.

The "Maple Leaf Rag" is a multi-strain ragtime march with athletic bass lines and offbeat melodies. Each of the four parts features a recurring theme and a striding bass line with copious seventh chords. The piece may be considered the "archetypal rag" due to its influence on the genre; its structure was the basis for many other rags, including "Sensation" by Joseph Lamb.

It is more carefully constructed than almost all the previous rags, and the syncopations, especially in the transition between the first and second strain, were novel at the time.

Generally, the "Maple Leaf Rag" is considered moderately difficult to play; a pianist must have very good coordination in the left hand to perform it successfully, particularly for the trio, which involves leaps of two octaves. When it was published, it was considered significantly more difficult than the average Tin Pan Alley and early ragtime sheet music common at the time.