The soprano trombone (sometimes called a slide trumpet or slide cornet, especially in jazz) is the soprano instrument in the trombone family of brass instruments, pitched in B♭ an octave above the tenor trombone. As the bore, bell and mouthpiece are similar to the B♭ trumpet, it tends to be played by trumpet players rather than trombonists. Compared to tenor, bass, or even uncommon alto, the soprano is a rare trombone. Seldom used in classical music since its first known appearance in 1677, it survived principally in the trombone ensembles of Moravian Church music. During the 20th century some soprano trombones—dubbed slide cornets—were made as novelties or for use by jazz trumpet players including Louis Armstrong and Dizzy Gillespie. A small number of contemporary proponents of the instrument include jazz artists Wycliffe Gordon and Christian Scott, and classical trumpeter Torbjörn Hultmark, who advocates for its use as an instrument for young children to learn the trombone.

Whether the soprano trombone was ever widely used in history is still a matter for debate. The earliest surviving instrument was made in 1677, held by the Landesmuseum in Linz. German Baroque composer Johann Sebastian Bach composed three cantatas (BWV 2, 21 & 38) around 1723 with four trombone parts; the highest was written in soprano clef, for a diskant-posaune (lit. 'descant trombone').

The soprano trombone was used in German-speaking countries to play the treble part in chorales, and this tradition survives in the trombone choirs of Moravian Church music. Outside of this, there is little evidence of the instrument being employed in musical ensembles or written works since the 18th century. This may have been because the Stadtpfeiffer (lit. 'town pipers'), who were trained to play all instruments, found fast and high (soprano) passages easier to play on the cornett.

Soprano trombone is seldom mentioned in the major orchestration treatises of the 19th century. German musicologist Adolf Bernhard Marx (1847) and English music scholar Ebenezer Prout (1897) only mention the soprano to state that it is considered obsolete, and French organist and composer Charles-Marie Widor in his 1904 treatise only mentioned that some manufacturers were still making them, while describing the alto as obsolete.

From 1900 through to the 1930s some soprano trombones—dubbed slide cornets—were made, mainly for jazz, by American manufacturers C. G. Conn, Buescher, and H. N. White. These instruments used tuning in the slide, rather than on the bow of the bell section. Later, Getzen produced an inexpensive slide trumpet in the 1960s. These were used by a few jazz trumpet players like Louis Armstrong, Bobby Hackett and Dizzy Gillespie, but otherwise were not widely adopted. In the 1970s and 80s, Los Angeles instrument makers Robb Stewart, Larry Minick, and Dominic Calicchio were making soprano trombones for local players including Bob and Chuck Findley, Eugene Lebeaux, and players in Moravian trombone choirs.

The B♭ soprano trombone is built with dimensions similar to the B♭ trumpet. The bore size is between 0.450 and 0.470 inches (11.4 and 11.9 mm), and the bell is 5 to 6 inches (130 to 150 mm) in diameter. It usually takes a trumpet mouthpiece, although some instruments are made with a smaller shank to take a cornet mouthpiece. The slide of a soprano trombone is much shorter than that of a standard tenor trombone, with the slide positions only half the distance apart.

Soprano trombones are made by several trombone manufacturers, often as inexpensive novelty instruments, although high quality professional instruments are made by Kanstul, Miraphone, Thein and others.

Californian instrument makers Larry Minick and Robb Stewart were making soprano trombones to order in the 1980s, some of which included an F attachment, a valve operated with a left thumb lever or trigger similar to those found on larger trombones. In the early 2010s, trumpeter Torbjörn Hultmark of the Royal College of Music commissioned a soprano trombone with an F valve, built by German maker Thein Brass. Helmut Voigt, another German manufacturer, also makes a soprano with an F valve.

Trombones smaller than the soprano have only been built since the 1950s, when they first appeared as novelty or "show" instruments.

The sopranino trombone in E♭, a fourth higher than the soprano and an octave above the alto, exists only in small numbers custom made for Moravian churches in the United States.

The piccolo trombone in B♭ is an octave above the soprano. It is essentially a piccolo trumpet with a slide instead of valves, and is used with a piccolo trumpet mouthpiece. Bore sizes are 0.460 inches (11.7 mm) or smaller, with bells approximately 4 inches (10 cm) in diameter. The piccolo is offered by Thein, Chinese manufacturer Jinbao, and Wessex. Thein also make a novelty piccolino trombone in F, a fifth higher than the B♭ piccolo, originally made for the German Brass ensemble.

The soprano trombone's similarity to the trumpet—its high pitch, mouthpiece size and narrow embouchure—means it is usually played by trumpeters. The player must combine both trumpet playing and trombone slide techniques to control intonation and note selection accuracy.