A preservative is a substance or a chemical that is added to products such as food products, beverages, pharmaceutical drugs, paints, biological samples, cosmetics, wood, and many other products to prevent decomposition by microbial growth or by undesirable chemical changes. In general, preservation is implemented in two modes, chemical and physical. Chemical preservation entails adding chemical compounds to the product. Physical preservation entails processes such as refrigeration or drying. Preservative food additives reduce the risk of foodborne infections, decrease microbial spoilage, and preserve fresh attributes and nutritional quality. Some physical techniques for food preservation include dehydration, UV-C radiation, freeze-drying, and refrigeration. Chemical preservation and physical preservation techniques are sometimes combined.

संरक्षक या परिरक्षी (preservative) ऐसे प्राकृतिक या मानवकृत रसायन को कहते हैं जिसे कुछ मात्रा में डालने से खाना, औषधि, रंग, लकड़ी, जीववैज्ञानिक वस्तुएँ व अन्य चीजें कीटाणुओं के प्रभाव या अनचाहे रासायनिक बदलाव से ख़राब होने से सुरक्षित की जाती हैं।