<p>Ensuring access to clean water through environmentally responsible methods has become a global priority. Chitosan, a biodegradable polymer sourced from natural chitin, has gained increasing attention for its potential as a green flocculant in water treatment. This mini-review summarises recent developments in the use of chitosan-based materials for contaminant removal via flocculation. Key factors, including the polymer’s molecular characteristics, functional groups, and chemical modifications, are discussed concerning their impact on flocculation efficiency. The review also outlines how chitosan and its derivatives have been tailored to enhance the removal of turbidity, dyes, heavy metals, and emerging pollutants, such as microplastics. Its low toxicity, biodegradability, and origin from renewable resources make it an ideal candidate for sustainable water purification technologies. Additionally, the review addresses current limitations in practical applications and identifies research directions to improve scalability and performance. By harnessing materials derived from nature to restore natural ecosystems, chitosan represents a promising step toward eco-conscious water management solutions.</p> Graphical Abstract <p></p>