The article provides a comprehensive overview of the current understanding of neutron star masses and radii, highlighting recent advancements in both observational techniques and theoretical modeling. The authors discuss the rapid increase in the discovery rate and precise timing of radio pulsars in binaries, which has led to a significant number of mass measurements. These measurements show that the neutron star mass distribution is broader than previously thought, with three known pulsars now firmly in the 1.9 – 2.0 $M_{\odot}$ range. For radii, large, high-quality datasets from X-ray satellites and improved theoretical modeling have placed the radii in the 9.9 – 11.2 km range, reducing uncertainties due to better understanding of systematic errors. The combination of these discoveries has made substantial progress in understanding the composition and bulk properties of cold nuclear matter at densities higher than that of the atomic nucleus, addressing a major unsolved problem in modern physics. The article also discusses the role of neutron stars in various astrophysical phenomena, such as gravitational wave sources and supernova explosions, and the impact of their properties on these events. The review covers various techniques used to measure neutron star masses and radii, including radio pulsar timing, double neutron star systems, millisecond pulsars, and X-ray binaries. It highlights the importance of different populations of neutron stars and the challenges and advancements in each area. The article concludes by discussing the maximum mass of neutron stars and the implications for the equation of state of dense matter.The article provides a comprehensive overview of the current understanding of neutron star masses and radii, highlighting recent advancements in both observational techniques and theoretical modeling. The authors discuss the rapid increase in the discovery rate and precise timing of radio pulsars in binaries, which has led to a significant number of mass measurements. These measurements show that the neutron star mass distribution is broader than previously thought, with three known pulsars now firmly in the 1.9 – 2.0 $M_{\odot}$ range. For radii, large, high-quality datasets from X-ray satellites and improved theoretical modeling have placed the radii in the 9.9 – 11.2 km range, reducing uncertainties due to better understanding of systematic errors. The combination of these discoveries has made substantial progress in understanding the composition and bulk properties of cold nuclear matter at densities higher than that of the atomic nucleus, addressing a major unsolved problem in modern physics. The article also discusses the role of neutron stars in various astrophysical phenomena, such as gravitational wave sources and supernova explosions, and the impact of their properties on these events. The review covers various techniques used to measure neutron star masses and radii, including radio pulsar timing, double neutron star systems, millisecond pulsars, and X-ray binaries. It highlights the importance of different populations of neutron stars and the challenges and advancements in each area. The article concludes by discussing the maximum mass of neutron stars and the implications for the equation of state of dense matter.