体素或立体像素(voxel)，是体积像素(volume pixel)的简称。概念上类似二维空间的最小单位——像素，像素用在二维电脑图像的影像数据上。体积像素一如其名，是数字数据于三维空间分割上的最小单位，应用于三维成像、科学数据与医学影像等领域。有些真正的三维显示器运用体素来描述它们的分辨率，举例来说：可以显示512×512×512体素的显示器。

如同像素，体素本身并不含有空间中位置的数据(即它们的座标)，然而却可以从它们相对于其他体素的位置来推敲，意即它们在构成单一张体积影像的数据结构中的位置。

A voxel represents a value on a regular grid in three-dimensional space. As with pixels in a bitmap, voxels themselves do not typically have their position (their coordinates) explicitly encoded along with their values. Instead, the position of a voxel is inferred based upon its position relative to other voxels (i.e., its position in the data structure that makes up a single volumetric image). In contrast to pixels and voxels, points and polygons are often explicitly represented by the coordinates of their vertices. A direct consequence of this difference is that polygons are able to efficiently represent simple 3D structures with lots of empty or homogeneously filled space, while voxels are good at representing regularly sampled spaces that are non-homogeneously filled.