概率论中，样本空间是一个实验或随机试验所有可能结果的集合，通常用S,Ω,U来表示。例如，如果抛掷一枚硬币，那么样本空间就是集合{正面，反面}。如果投掷一个骰子，那么样本空间就是{1,2,3,4,5,6}。样本空间的任何一个子集都被称为一个事件。如果一个子集只有一个元素，那这个子集被称为基本事件。

有些实验有2个或多个可能的样本空间。例如，从52张扑克牌中随机抽出一张，一个可能的样本空间是数字（A到K），另外一个可能的样本空间是花色（黑桃，红桃，梅花，方块）。如果要完整的描述一张牌，就需要同时给出数字和花色，这时的样本空间可以通过构建上述两个样本空间的笛卡儿乘积来得到。

In probability theory, the sample space or universal sample space, often denoted S, Ω, or U (for "universe"), of an experiment or random trial is the set of all possible outcomes. For example, if the experiment is tossing a coin, the sample space is the set {head, tail}. For tossing a single six-sided die, the sample space is {1, 2, 3, 4, 5, 6}^[1]. For some kinds of experiments, there may be two or more plausible sample spaces available. For example, when drawing a card from a standard deck of 52 playing cards, one possibility for the sample space could be the rank (Ace through King), while another could be the suit (clubs, diamonds, hearts, or spades).