油母质（英语：Kerogen）又音译做干酪根或依外观称为油田沥青，是存在于沉积岩（尤其是页岩）之中由有机物经过复杂的化石化作用所形成的混合有机物物质。它不溶于普通的有机溶剂是因为其成分化合物的高分子量（向上达到1,000道尔顿或1000 Da；1Da=1原子质量单位）。可溶部分被称为沥青。当在地壳中的油母质被加热到合适高温的时候，一些类型的油母质释放出石油或者天然气，统称为烃（化石燃料）。

油母质的英文命名“Kerogen”是由苏格兰有机化学家亚历山大·克拉姆·布朗在1906年推出。

Kerogen (Greek κηρός "wax" and -gen, γένεση "birth") is a mixture of organic chemical compounds that make up a portion of the organic matter in sedimentary rocks. It is insoluble in normal organic solvents because of the high molecular weight (upwards of 1,000 daltons or 1000 Da; 1Da= 1 atomic mass unit) of its component compounds. The soluble portion is known as bitumen. When heated to the right temperatures in the Earth's crust, (oil window c. 50–150 °C, gas window c. 150–200 °C, both depending on how quickly the source rock is heated) some types of kerogen release crude oil or natural gas, collectively known as hydrocarbons (fossil fuels). When such kerogens are present in high concentration in rocks such as shale, they form possible source rocks. Shales rich in kerogens that have not been heated to a warmer temperature to release their hydrocarbons may form oil shale deposits.