This mini-review article, "From Nature for Nature: Chitosan-based Materials for Clean Water by Flocculation," which focuses on the use of chitosan, a biodegradable polymer derived from natural chitin, as a sustainable flocculant for water treatment. The source explains that global freshwater scarcity makes it a priority to find environmentally responsible methods to remove contaminants like heavy metals, dyes, microplastics, and turbidity. The review details the fundamental flocculation mechanism of chitosan, which primarily involves charge neutralisation and polymer bridging, and discusses how factors such as pH, dosage, and molecular weight affect its performance. Critically, the text highlights the development of various advanced chitosan materials—including functionalised, magnetic, and hydrogel composites—to overcome the limitations of bare chitosan, such as low solubility and pH sensitivity. Finally, the review addresses the practical challenges of using chitosan, such as its high cost and the need for scalable production and regeneration strategies.