在粒子物理学中，ρ介子是一种寿命短的重子，它的同位旋三重态是由ρ+、ρ0及ρ−所表示。除了π介子及K介子，ρ介子是最轻的强相互作用粒子，三种态的质量都大概在770 MeV左右。ρ+及ρ0间应该有一个小的质量差，是由粒子自身的电磁能所造成的，同时轻夸克质量所造成的同位旋破缺也会带来一点的质量差；然而，现时的实验指出这样的质量差差额上限为0.7 MeV。

ρ介子的寿命很短，其衰变宽度约为145 MeV，还有很奇怪的一点是，ρ介子的共振宽度并不能用布莱特-维格纳分布(Breit-Wigner distribution)来描述。ρ介子主衰变模式的产物为一对π介子，其分支比达99.9%。

In particle physics, a rho meson is a short-lived hadronic particle that is an isospin triplet whose three states are denoted as ρ+, ρ0 and ρ−. After the pions and kaons, the rho mesons are the lightest strongly interacting particle with a mass of roughly 6990123367589499000♠770 MeV for all three states. There should be a small mass difference between the ρ+ and the ρ0 that can be attributed to the electromagnetic self-energy of the particle as well as a small effect due to isospin breaking arising from the light quark masses; however, the current experimental limit is that this mass difference is less than 6987112152354090000♠0.7 MeV.