性学（Sexual science or Sexology），又称性科学，是关于人类的性表象的系统研究。它的范畴涵盖了性的所有面向，包括了所谓的正常的性以及性心理变态。

现代性学是一门跨学科领域，它使用了来自不同领域的研究方式，包括生物学、医学、心理学、统计学、流行病学、社会学以及有时候会使用犯罪学来研究性学的议题。性学研究人类的性成长、性关系的发展、性行为的机制以及性功能障碍等。它也会研究特别群体中的性，比如身心障碍者、儿童和老人的性。它也研究性病理学，比如性亢奋和性虐待。

要注意的是，性学是一种描述性的学问，而非指示性的学问——性学是去试图纪录事实，而非去指点出什么行为是合适或道德的。因此，性学时常会带来争议，有些人支持性学研究，而有些人则认为性学刺探了对一个科学研究来说太过于私密、神圣、或者恶心的事物上。

Sexology is the scientific study of human sexuality, including human sexual interests, behaviors and functions. The term sexology does not generally refer to the non-scientific study of sexuality, such as political science or social criticism.

Sexologists apply tools from several academic fields, such as biology, medicine, psychology, epidemiology, sociology and criminology. Topics of study include sexual development (puberty), sexual orientation and gender identity, sexual relationships and sexual activity, paraphilias and atypical sexual interests, as well as the sexualities of special groups, such as child sexuality, adolescent sexuality, sexuality among the elderly and the disabled. The sexological study of sexual dysfunctions and disorders, including erectile dysfunction, anorgasmia, and pedophilia, are also mainstays. The field also employs specific therapeutic models to help patients dealing with various issues, such as the PLISSIT model.