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 huge molecular weight (upwards of 1,000) of its component compounds. The soluble portion is known as bitumen. When heated to the right temperatures in the Earth's crust, some types of kerogen release oil or gas, collectively known as hydrocarbons (fossil fuels). When such kerogens are present in high concentration in rocks such as shale, and have not been heated to a sufficient temperature to release their hydrocarbons, they may form oil shale deposits.

Kerogen from the Green River Formation oil shale deposit of western USA has the chemical composition C₂₁₅H₃₃₀O₁₂N₅S.