前奏曲 是一种短乐曲。前奏曲以前只是组曲之前的器乐引子，在演奏之前一般演奏家要即兴演奏一小段，逐渐演变成一种艺术形式。前奏曲也用于歌剧以代替序曲，曲式自由，一般取材于剧中的音乐，在正场前使用。17世纪时出版商在出版乐谱以前会印发前奏曲作为广告。

序曲与前奏曲最大的差别，主要是前奏曲可放在各幕之前，但序曲只能放在第一幕之前，这是因为序曲是代表整部戏剧、歌剧或芭蕾的剧情，而前奏曲一般只代表各幕的剧情。此外，序曲一般会先完整演奏结束，之后才正式进入第一幕；而前奏曲则是在乐曲快结束时，布幕便开始缓缓升起，直接把观众情绪导入该幕的剧情内，所以前奏曲也常常直接衔接该幕的第一首曲子，而并无明显结束的乐句。

A prelude (Germ. Präludium or Vorspiel; Lat. praeludium; Fr. prélude; It. preludio"; Pt. "prelúdio) is a short piece of music, the form of which may vary from piece to piece. The prelude may be thought of as a preface. While, during the Baroque era, for example, it may have served as an introduction to succeeding movements of a work that were usually longer and more complex, it may also have been a standalone piece of work during the Romantic era. It generally features a small number of rhythmic and melodic motifs that recur through the piece. Stylistically, the prelude is improvisatory in nature. The prelude also may refer to an overture, particularly to those seen in an opera or an oratorio.