Flexible and portable devices are a mainstream direction in modern electronics and related multidisciplinary fields. To this end, they are generally required to be stretchable to satisfy various substrates. [1,2] As a result, stretchable devices, such as electrochemical supercapacitors, [3][4][5][6] lithium-ion batteries, [7] organic solar cells, [8] organic light-emitting diodes, [9,10] field-effect transistors, [11] and artificial skin sensors [12] have been widely studied. However, these stretchable devices are made in a conventional planar format that has largely hindered their development. For the portable applications, the devices need to be lightweight and small, though it is difficult for them to be made into efficient microdevices. In particular, it is challenging or even impossible for them to be used in electronic circuits and textiles that are urgently required also in a wide variety of other fields, such as microelectronic applications.Recently, some attempts have been made to fabricate wire-shaped microdevices, such as electrochemical supercapacitors. They have been generally produced by twisting two fiber electrodes with electrolytes coated on the surface. [13][14][15][16][17][18][19] Several examples have been also successfully shown to make fiber-shaped supercapacitors with a coaxial structure. [20,21] Compared with their planar counterparts, the wire or fiber shape enables promising advantages such as being lightweight and woven into textiles. Although the wire and fiber-shaped supercapacitors are also flexible with high electrochemical performance, they are not stretchable, which is critically important for many applications. For instance, the resulting electronic textiles could easily break during the use if they were not stretchable.To the best of our knowledge, herein we have, for the first time, developed a novel family of highly stretchable, fibershaped high-performance supercapacitors. Aligned carbon nanotube (CNT) sheets that are sequentially wrapped on an elastic fiber serve as two electrodes. The use of aligned CNT sheets offers combined remarkable properties including high flexibility, tensile strength, electrical conductivity, and