The first inductively coupled plasma optical emission spectroscopy (ICP-OES) instrument became commercially available more than 50 years ago, in 1974. Over recent decades, it has emerged as a key spectroscopic technique for analyzing numerous elements, offering a powerful tool for elemental analysis at milliparticle (ppm) and parts-per-billion (ppb) levels. This comprehensive review highlights the applications of ICP-OES across various scientific disciplines, with a particular focus on pharmaceutical technology, illustrated through a practical solution.