Spectroscopy plays a pivotal role in discerning the chemical and biochemical compositions of analytes, significantly impacting chemical and material analysis, disease diagnosis, environmental monitoring, and space exploration. Despite the widespread demand for optical spectrometers in both industry and academia, their deployment in many practical applications is hindered by the high costs, large footprints, and mechanical vibration sensitivity of conventional spectrometers. These problems are addressed by integrated optical spectrometers. Silicon photonics offers a potentially low‐cost platform for ultracompact integrated optical spectrometers, leveraging the complementary metal‐oxide‐semiconductor (CMOS) compatible fabrication technology and high flexibility in on‐chip light manipulation of high‐index waveguides. The integrated optical spectrometers on silicon photonics platforms provide promising solutions for developing ultra‐compact and cost‐effective spectral analyzers in various applications. This review paper overviews recent advancements in integrated optical spectrometers on silicon photonics platforms over the past decades, focusing on their fundamental principles, design methodologies, spectral performances, and potential applications. By blending foundational knowledge with cutting‐edge research, this review aims to involve researchers from different fields, including spectroscopy, materials science, astronomy, environmental engineering, and beyond.