预防医学是指以预防疾病的发生，来代替对疾病的治疗，这与华人「预防胜于治疗」的观念相符，又与中医「上医治未病」的境界相呼应。

预防医学着重在保持、促进与维护普罗大众、特定群体或一般个人的健康，并包括预防传染病、疾病、残疾、癌症、其他身体组织变异、与过早死亡的发生，因此涉及多个科学、医学与公共卫生领域，包括有：

Preventive healthcare (alternately preventive medicine or prophylaxis) consists of measures taken for disease prevention, as opposed to disease treatment. Just as health encompasses a variety of physical and mental states, so do disease and disability, which are affected by environmental factors, genetic predisposition, disease agents, and lifestyle choices. Health, disease, and disability are dynamic processes which begin before individuals realize they are affected. Disease prevention relies on anticipatory actions that can be categorized as primal, primary, secondary, and tertiary prevention.