Porous organic polymers (POPs) are organic macromolecules that are considered emerging materials because of their high specific surface areas, tunable porosities, low densities, high chemical and thermal stabilities, variable compositions, convenient post-functionalization, extended π-conjugations, and their high contents of carbon, nitrogen, oxygen, and other non-metallic atoms. POPs have been classified into four types: covalent triazine frameworks (CTFs), hypercrosslinked polymers (HCPs), covalent organic frameworks (COFs), and conjugated microporous polymers (CMPs). These materials have potential applications in, for example, gas capture/separation, energy storage, H₂ production from water, photocatalysis, chemical sensing, perovskite solar cells, water treatment, optical devices, and biomedicine. In this review, we provide an overview of recent reports describing the preparation and various applications of POPs.