Plasmonic surface lattice resonances (SLRs) are collective optical phenomena arising from the coupling of localized surface plasmons (LSPs) in ordered arrays of metal nanoparticles. When arranged in a periodic structure, these nanoparticles can scatter light to produce diffracted waves that couple the localized plasmon resonances, leading to a dramatic narrowing of the resonance width to 1–2 nm, a significant improvement over the >80 nm width of single-particle resonances. This phenomenon, known as plasmonic surface lattice resonances, has become a focal point in fundamental research and has shown promise in various practical applications, including communications, optoelectronics, photovoltaics, biosensing, and data storage. The review discusses the physical principles and properties of SLRs, including their resonance width, quality factors, and the conditions for their excitation in different experimental setups. It covers the effects of in-plane and out-of-plane polarizations, symmetric and asymmetric optical environments, substrate conductivity, and the presence of active or magnetic media. The review also highlights recent advancements in the application of SLRs in various fields, such as optical sensing, light emission, and the integration with two-dimensional materials. The review begins with an introduction to plasmonics, explaining the types of plasmon modes, including propagating surface plasmons (PSPs) and localized surface plasmons (LSPs), and the factors influencing their resonance widths. It then delves into early theoretical studies of diffraction-coupled LSPs, including the coupled dipole approximation and the role of array period. Experimental observations of SLRs are discussed, including the use of ellipsometry and the conditions necessary for their detection. The review also explores the properties of SLRs, such as phase singularities, their role in optical sensing, and their potential in applications like biosensing, photovoltaics, and photocatalysis. The review concludes with a summary of the key findings and the importance of SLRs in advancing the field of plasmonics, emphasizing their potential for future technological applications.Plasmonic surface lattice resonances (SLRs) are collective optical phenomena arising from the coupling of localized surface plasmons (LSPs) in ordered arrays of metal nanoparticles. When arranged in a periodic structure, these nanoparticles can scatter light to produce diffracted waves that couple the localized plasmon resonances, leading to a dramatic narrowing of the resonance width to 1–2 nm, a significant improvement over the >80 nm width of single-particle resonances. This phenomenon, known as plasmonic surface lattice resonances, has become a focal point in fundamental research and has shown promise in various practical applications, including communications, optoelectronics, photovoltaics, biosensing, and data storage. The review discusses the physical principles and properties of SLRs, including their resonance width, quality factors, and the conditions for their excitation in different experimental setups. It covers the effects of in-plane and out-of-plane polarizations, symmetric and asymmetric optical environments, substrate conductivity, and the presence of active or magnetic media. The review also highlights recent advancements in the application of SLRs in various fields, such as optical sensing, light emission, and the integration with two-dimensional materials. The review begins with an introduction to plasmonics, explaining the types of plasmon modes, including propagating surface plasmons (PSPs) and localized surface plasmons (LSPs), and the factors influencing their resonance widths. It then delves into early theoretical studies of diffraction-coupled LSPs, including the coupled dipole approximation and the role of array period. Experimental observations of SLRs are discussed, including the use of ellipsometry and the conditions necessary for their detection. The review also explores the properties of SLRs, such as phase singularities, their role in optical sensing, and their potential in applications like biosensing, photovoltaics, and photocatalysis. The review concludes with a summary of the key findings and the importance of SLRs in advancing the field of plasmonics, emphasizing their potential for future technological applications.