MgCl₂ supported Ziegler–Natta (Z–N) catalysts have emerged as the most exciting chemical process for polyolefin technology, which is responsible for the production of ∼150 million tons of polyolefin (polyethylene and polypropylene) per annum. However, fundamental chemistry of Z–N catalysts is not fully understood yet due to their multi-component nature as well as heterogeneous systems. Therefore, in this review, we have highlighted the chronological development of a heterogeneous Z–N catalyst and its polymerization (ethylene, propylene and 1-butene) process including termination steps. Then, we have discussed different structural and chemical aspects of the catalyst support, catalytically active sites, cocatalyst, internal/external electron donors and their different combinations. In the last two decades, density functional theory (DFT) has been employed in Z–N systems to strengthen the experimental work as well as to understand mechanistic aspects of Z–N systems. Future directions of Z–N catalysts have also been discussed.