Recent progress in sulfur-containing high refractive index (HRI) polymers for optical applications is reviewed. Sulfur, with its high molar refraction, plays a crucial role in enhancing the refractive index of polymers. Sulfur-containing polymers have been extensively studied for decades, with recent focus on incorporating sulfur into the polymer backbone to improve thermal resistance, mechanical strength, processability, solubility, and flame resistance. Sulfur allows for extended conjugated electron systems, enabling the fabrication of sustainable and efficient display technologies. Sulfur-containing polymers find applications in various fields, including cathode materials for lithium-ion batteries, memory devices, conducting polymers, and optical materials. Polysulfones and polysulfides are high-industrial importance sulfur-containing polymers. Sulfur-containing polythiophene films exhibit electrochromism, chemochromism, or sensory characteristics. The combination of conjugation and high molar refraction of sulfur gives polythiophenes superiority in terms of refractive index (RI). Poly(3-alkylthiophenes) (P3AT) provide immense scope in organic field effect transistors (OFETs) and photovoltaic devices due to high field effect mobilities. Polarized electroluminisence is boosted due to the strong anisotropic structure of conjugated polykylthiophenes. The alkyl side-chain length, solvent, casting method, and thermal history play a vital role in field effect mobility. Sulfur-containing polymers have numerous applications, making it challenging to summarize them under one topic. Polymer materials have attracted great attention for optical devices due to their diverse applicability and low installation cost. High refractive index (n) polymers have a wide range of applications, including optical elements made by nanoimprinting, substrates with high performance in display technologies, optical coatings in organic light emitting diodes (OLED), antireflective coatings for lenses, microlens modules for image sensors, and immersion fluids and resists in 193 nm immersion lithography technologies. The refractive index of a polymer can be calculated using the Lorentz–Lorenz equation. The Abbe number, which measures the dispersion of a material, is also discussed. Birefringence, which is the difference in refractive indices for in-plane and out-of-plane orientations, is an important factor in optical devices. Optical transparency is also crucial for polymer applications. High refractive index polymers are essential for nanoimprinted optical circuits, OLEDs, image sensors, and antireflective coatings. The synthesis of sulfur-containing polymers involves various methods, including chain-growth and step-growth polymerization. Inverse vulcanization is a unique method for preparing high-resolution (RI) polymers with sulfur in their backbones. Sulfur-containing polyethers, polyimides, polyRecent progress in sulfur-containing high refractive index (HRI) polymers for optical applications is reviewed. Sulfur, with its high molar refraction, plays a crucial role in enhancing the refractive index of polymers. Sulfur-containing polymers have been extensively studied for decades, with recent focus on incorporating sulfur into the polymer backbone to improve thermal resistance, mechanical strength, processability, solubility, and flame resistance. Sulfur allows for extended conjugated electron systems, enabling the fabrication of sustainable and efficient display technologies. Sulfur-containing polymers find applications in various fields, including cathode materials for lithium-ion batteries, memory devices, conducting polymers, and optical materials. Polysulfones and polysulfides are high-industrial importance sulfur-containing polymers. Sulfur-containing polythiophene films exhibit electrochromism, chemochromism, or sensory characteristics. The combination of conjugation and high molar refraction of sulfur gives polythiophenes superiority in terms of refractive index (RI). Poly(3-alkylthiophenes) (P3AT) provide immense scope in organic field effect transistors (OFETs) and photovoltaic devices due to high field effect mobilities. Polarized electroluminisence is boosted due to the strong anisotropic structure of conjugated polykylthiophenes. The alkyl side-chain length, solvent, casting method, and thermal history play a vital role in field effect mobility. Sulfur-containing polymers have numerous applications, making it challenging to summarize them under one topic. Polymer materials have attracted great attention for optical devices due to their diverse applicability and low installation cost. High refractive index (n) polymers have a wide range of applications, including optical elements made by nanoimprinting, substrates with high performance in display technologies, optical coatings in organic light emitting diodes (OLED), antireflective coatings for lenses, microlens modules for image sensors, and immersion fluids and resists in 193 nm immersion lithography technologies. The refractive index of a polymer can be calculated using the Lorentz–Lorenz equation. The Abbe number, which measures the dispersion of a material, is also discussed. Birefringence, which is the difference in refractive indices for in-plane and out-of-plane orientations, is an important factor in optical devices. Optical transparency is also crucial for polymer applications. High refractive index polymers are essential for nanoimprinted optical circuits, OLEDs, image sensors, and antireflective coatings. The synthesis of sulfur-containing polymers involves various methods, including chain-growth and step-growth polymerization. Inverse vulcanization is a unique method for preparing high-resolution (RI) polymers with sulfur in their backbones. Sulfur-containing polyethers, polyimides, poly