Strong light-matter coupling in van der Waals materials has become a focal point in two-dimensional (2D) materials research due to their potential for isolating and combining diverse atomic layers. Atomically thin transition metal dichalcogenides (TMDs) are particularly promising due to their exceptional electronic and optical properties. When integrated with optical cavities, TMDs enable strong light-matter coupling, offering opportunities for exploring novel polaritonic physics and devices. This review discusses recent advances in TMD-based strong light-matter coupling, focusing on various optical structures such as Fabry-Perot cavities, photonic crystals, and plasmonic nanocavities. It also presents intriguing properties and applications of TMD polaritons, including valley polarization, nonlinearities, and electrical-magnetic tuning. The review highlights the potential of TMDs for room-temperature polariton devices and explores future directions in the study of strong light-matter coupling in van der Waals materials. TMDs, with their unique spin-valley locking and strong excitonic effects, offer new opportunities for polarization-selective polaritonic devices and enhanced nonlinear interactions. Recent progress includes the realization of room-temperature polariton light-emitting diodes (LEDs) and the observation of polariton condensation in TMD systems. The review also discusses the potential of TMD-based polaritonic devices, including polariton lasers, spin transistors, and all-optical switches. The study of TMD polaritons in various optical structures has led to significant advances in understanding their properties and applications, with promising prospects for future developments in polaritonic physics and technology.Strong light-matter coupling in van der Waals materials has become a focal point in two-dimensional (2D) materials research due to their potential for isolating and combining diverse atomic layers. Atomically thin transition metal dichalcogenides (TMDs) are particularly promising due to their exceptional electronic and optical properties. When integrated with optical cavities, TMDs enable strong light-matter coupling, offering opportunities for exploring novel polaritonic physics and devices. This review discusses recent advances in TMD-based strong light-matter coupling, focusing on various optical structures such as Fabry-Perot cavities, photonic crystals, and plasmonic nanocavities. It also presents intriguing properties and applications of TMD polaritons, including valley polarization, nonlinearities, and electrical-magnetic tuning. The review highlights the potential of TMDs for room-temperature polariton devices and explores future directions in the study of strong light-matter coupling in van der Waals materials. TMDs, with their unique spin-valley locking and strong excitonic effects, offer new opportunities for polarization-selective polaritonic devices and enhanced nonlinear interactions. Recent progress includes the realization of room-temperature polariton light-emitting diodes (LEDs) and the observation of polariton condensation in TMD systems. The review also discusses the potential of TMD-based polaritonic devices, including polariton lasers, spin transistors, and all-optical switches. The study of TMD polaritons in various optical structures has led to significant advances in understanding their properties and applications, with promising prospects for future developments in polaritonic physics and technology.