数学上，勒贝格测度是赋予欧几里得空间的子集一个长度、面积、或者体积的标准方法。它广泛应用于实分析，特别是用于定义勒贝格积分。可以赋予一个体积的集合被称为勒贝格可测；勒贝格可测集A的体积或者说测度记作λ(A)。一个值为∞的勒贝格测度是可能的，但是即使如此，在假设选择公理成立时，R的所有子集也不都是勒贝格可测的。不可测集的“奇特”行为导致了巴拿赫-塔斯基悖论这样的命题，它是选择公理的一个结果。

In measure theory, the Lebesgue measure, named after French mathematician Henri Lebesgue, is the standard way of assigning a measure to subsets of n-dimensional Euclidean space. For n = 1, 2, or 3, it coincides with the standard measure of length, area, or volume. In general, it is also called n-dimensional volume, n-volume, or simply volume. It is used throughout real analysis, in particular to define Lebesgue integration. Sets that can be assigned a Lebesgue measure are called Lebesgue measurable; the measure of the Lebesgue measurable set A is denoted by λ(A).