This document summarizes a seminar presentation on fluid couplings. It includes sections on the introduction, history, construction, operation, explanation, advantages, and applications of fluid couplings. A fluid coupling transmits rotating mechanical power between two shafts without a direct mechanical connection using an intermediate fluid like oil. It was invented in the early 20th century by German engineer Hermann Föttinger. A fluid coupling consists of a pump impeller on the driving shaft and a turbine runner on the driven shaft enclosed in a housing filled with fluid.