The search for safe, sustainable, and effective food preservatives has shifted strongly toward natural alternatives, driven by consumer demand for healthier products. These compounds, sourced from plants, microorganisms, animals, and algae, show antimicrobial, antioxidant, and enzyme-inhibiting properties. For example, plant phenolic compounds can cut microbial counts by more than 90%, while essential oils from thyme, rosemary, or oregano inhibit foodborne pathogens such as Listeria monocytogenes and Escherichia coli at very low concentrations. Similarly, peptides from lactic acid bacteria and marine organisms reduce lipid oxidation in meats by over 80%. This chapter reviews natural preservatives, starting with their diverse sources, then addressing innovative extraction methods such as supercritical fluid, ultrasonic-assisted, and enzymatic techniques, which preserve the integrity of bioactive molecules. Characterization methods like HPLC, GC-MS, and NMR confirm chemical structures and active compounds, allowing accurate evaluation of antimicrobial and antioxidant functions. This chapter also highlights synergistic effects, where combinations of compounds from one or multiple sources work more effectively together. Applications include essential oils, plant polyphenols, peptides, and natural acids, all proven to protect against bacteria, fungi, and yeasts. Challenges such as volatility, instability, or sensory impacts are discussed, along with encapsulation technologies that help maintain stability. In conclusion, natural preservatives represent a promising future for safe, sustainable food preservation.