Petro Chemistry- A chemical product that is derived from crude oil, even if most of the identical chemical compounds are also acquired from other fossil fuels that is coal and natural gas, or from renewable sources like corn, sugar cane, and other types of biomass. In the present context of petrochemicals, this chapter concentrates on organic hydrocarbon compounds that are not burned as a fuel and are basically called crude oil products. On the basis of chemical structure, petrochemicals are classified into three orders of petro chemistry products (i) olefin derivatives, (ii) aromatic derivatives, and (iii) synthesis gas. Ethylene and propylene are the important part of olefin derivatives which is the basic source in the preparation of different industrial chemicals and plastic products whereas butadiene is commonly used to make synthetic rubber. Benzene, toluene, and xylene isomers are vital elements of aromatic chemicals. These aromatic petrochemicals are used in assembling secondary products like synthetic detergents, plastic, and synthetic fibers. Synthetic gases having carbon monoxide and hydrogen which are commonly used to create ammonia and methanol are further used to generate other chemicals and synthetic material.