夸克偶素（英语：Quarkonium，复数为Quarkonia）指的是无味的介子，即是由夸克及其对应的反夸克所组成的。夸克偶素的例子有J/ψ介子（魅夸克偶素c c 的例子）及Υ介子（底夸克偶素b b 的例子）。由于顶夸克的质量很大，在能够生成束缚态之前，就已经通过电弱相互作用衰变掉，因此顶夸克偶素并不存在。一般夸克偶素一词只用于魅夸克偶素及底夸克偶素，不用于其他轻夸克－反夸克对。这样用是因为其他轻夸克（上、下及奇）实在比重夸克要轻得多。魅和底夸克与轻夸克间的巨大质量差，使得任一种味的夸克－反夸克对，都能有着相当分明的定义态。

In particle physics, quarkonium (from quark + onium, pl. quarkonia) designates a flavorless meson whose constituents are a quark and its own antiquark. Examples of quarkonia are the J/ψ meson (the ground state of charmonium, cc) and the ϒ meson (bottomonium, bb). Because of the high mass of the top quark, toponium does not exist, since the top quark decays through the electroweak interaction before a bound state can form. Usually quarkonium refers only to charmonium and bottomonium, and not to any of the lighter quark–antiquark states. This usage is because the lighter quarks (up, down, and strange) are much less massive than the heavier quarks, and so the physical states actually seen in experiments (η, η′, and π mesons) are quantum mechanical mixtures of the light quark states. The much larger mass differences between the charm and bottom quarks and the lighter quarks results in states that are well defined in terms of a quark–antiquark pair of a given flavor.