Controlled and sustained drug delivery has recently become the industry standard, and extensive research has been conducted in order to improve drug product effectiveness, reliability, and safety. The ‘in-situ gel' system has emerged as one of the best innovative drug delivery systems; its unique feature of ‘Sol to Gel' transition aids in the sustained and controlled release of drugs. A formulation that is in solution form before entering the body, but changes to gel form under certain physiological conditions, is known as an in-situ gelling system. The advantages of in-situ forming polymeric delivery systems, including simplicity of administration and reduced frequency of administration, increased patient compliance and comfort, have spurred attention. In-situ gels are a type of hydrogel that starts off as a solution and gels when exposed to bodily fluids or changes in pH. Guar gum, gellan gum, xanthan gum, carrageenan, xyloglucan, pectin, chitosan, and thiolated chitosan are some of the polymers employed in in-situ gelling systems. This review focused on introduction, advantages and disadvantages, approaches and mechanism, preparation methods, polymers used, characterization as well as applications.