Neoplasia (new growth in Latin) is abnormal, disorganized growth in a tissue or organ, usually forming a distinct mass. Such a growth is called a neoplasm, also known as a tumor.

Neoplasia is the correct, scientific term for diseases commonly called "cancer", "tumor" or "growth". Neoplasms can be benign or malignant lesions. Leiomyoma (fibroids of the uterus) and melanocytic nevi (beauty spots) are the most common types of neoplasms. They are both benign.

Neoplasia is a complex subject. This article is voluntarily kept short; a detailed discussion of neoplastic diseases can be found in the Cancer article.