夸克星（英语：Quark star）由奇异物质组成，是一种理论假设可能存在的引力致密星体，需要更多的观测数据及关键遗失环结理论推导来佐证其真实性。

实验验证方面，关键的奇异物质理论至今还是假说，至2013年五月为止，没有任何可能的夸克星类型被证实或理论可以完全自洽，基础成分「H双重子」亦未被寻获，最后一组对「H双重子」进行搜索实验的是日本KEK（高能加速器研究机构）与日本原子能研究开发机构（JAEA）的合作项目J-PARC，目前尚未有结论。

2013年6月17日，北京质谱仪BES III与日本KEK的Belle团队在研究疑似粲夸克偶素（Charmonium）的Y（4260）时，分别独立发现Zc（3900），实验报告于美国物理通信上发表，Zc（3900）的夸克态可能是ccud或是介子分子混杂态（hadron molecule），是目前迹象最明确有可能被正式认定的第一个四夸克态粒子（双夸克反双夸克态）。Zc（3900）如果确认成立，其意义十分重大，将正式确立多夸克态物理的成立，确认一整门新物理学的出现，多夸克态一旦成立，则夸克水平的星体均可能成立，但不见得是奇异夸克星，也有可能是混杂态夸克星或是孤子星产生机率更高，这对近代天体物理发展而言是一项很大的突破，一整个族系的多夸克态星体均有可能被列入天体物理的研究范围内。

A quark star is a hypothetical type of compact exotic star composed of quark matter. These are ultra-dense phases of degenerate matter theorized to form inside particularly massive neutron stars.

The hypothesis about quark stars was first proposed in 1965 by Soviet physicists D.D. Ivanenko and D.F. Kurdgelaidze. Their existence has not been confirmed theoretically or astronomically. The equation of state of quark matter is uncertain, as is the transition point between neutron-degenerate matter and quark matter. Theoretical uncertainties have precluded making predictions from first principles. Experimentally, the behaviour of quark matter is being actively studied with particle colliders, but this can only produce very hot (above 10 K) quark-gluon plasma blobs the size of atomic nuclei, which decay immediately after formation. The conditions inside compact stars with extremely high densities and temperatures well below 10 K, can not be recreated artificially so there are no known method to produce, store or study "cold" quark matter directly as it would be found inside quark stars. The theory predicts quark matter to possess some peculiar characteristics under these conditions.