The linea alba is the aponeurosis of the abdominal wall muscles in the median line and transmits the forces of the abdominal wall muscles, thus allowing the abdominal wall to be tightened. Its scissor-like structure allows changes in the volume of the abdominal cavity. The linea alba has a thickness of 900–2400 micrometers. The length of the linea alba varies according to habitus, body size, sex and posture. The width of the linea alba varies greatly. An excess width is referred to as rectus diastasis, but a generally valid definition of rectus diastasis is lacking and is highly dependent on the population studied. The linea alba is supplied with blood via perforators of the inferior and superior epigastric arteries. Microscopically, the linea alba can be divided into three layers. In this chapter, various aspects are discussed in more detail and in relation to their clinical significance.