Measurement of the state of polarization of light, emitted from different sources or scattered by various objects, is significant to astronomers, atmospheric scientists, biologists, chemists, physicists, and engineers, and has a wide range of important applications. Conventional optical polarimetry is based on discrete polarizing optical elements (POE), such as crystal polarizers and wave retarders. Integrated polarimeters (IPs) depart from this established practice in that they rely on photodectors only, and require no POE. An IP integrates the polarization analysis and photodetection functions in the detectors. Three IPs are discussed: (1) the rotating-detector ellipsometer (RODE), (2) the two-detector ellipsometer (TDE), and (3) the four-detector photopolarimeter (FDP), in ascending order of apparent complexity. RODE can measure the state of polarization of totally polarized light, except for handedness; TDE provides a fast measurement of the degree of linear polarization of light and can also be operated as a handedness-blind ellipsometer; and FDP measures all the four Stokes parameters of light which is generally partially elliptically polarized. The FDP has several important advantages: (1) It has no moving parts or modulators; (2) it has a rugged design of four solid-state detectors; (3) it uses efficiently all of the input light flux for polarization determination; and (4) it is readily interfaceable with an on-line microcomputer. Further extension of these concepts include the in-line light-saving IP, and IPs that use anisotropic photodetectors.