The seminal vesicles (also called vesicular glands, or seminal glands) are a pair of two convoluted tubular glands that lie behind the urinary bladder of some male mammals. They secrete fluid that partly composes the semen.

The vesicles are 5–10 cm in size, 3–5 cm in diameter, and are located between the bladder and the rectum. They have multiple outpouchings which contain secretory glands, which join together with the vas deferens at the ejaculatory duct. They receive blood from the vesiculodeferential artery, and drain into the vesiculodeferential veins. The glands are lined with column-shaped and cuboidal cells. The vesicles are present in many groups of mammals, but not marsupials, monotremes or carnivores.

Inflammation of the seminal vesicles is called seminal vesiculitis, most often is due to bacterial infection as a result of a sexually transmitted disease or following a surgical procedure. Seminal vesiculitis can cause pain in the lower abdomen, scrotum, penis or peritoneum, painful ejaculation, and blood in the semen. It is usually treated with antibiotics, although may require surgical drainage in complicated cases. Other conditions may affect the vesicles, including congenital abnormalities such as failure or incomplete formation, and, uncommonly, tumours.

The seminal vesicles have been described as early as the second century AD by Galen, although the vesicles only received their name much later, as they were initially described using the term from which the word prostate is derived.