In anatomy, a stoma (plural stomata or stomas) is any opening in the body. For example, a mouth, a nose, and an anus are natural stomata. Any hollow organ can be manipulated into an artificial stoma as necessary. This includes the esophagus, stomach, duodenum, ileum, colon, pleural cavity, ureters, urinary bladder, and renal pelvis. Such a stoma may be permanent or temporary.

Surgical procedures that involve the creation of an artificial stoma have names that typically end with the suffix "-ostomy", and the same names are also often used to refer to the stoma thus created. For example, the word "colostomy" often refers either to an artificial anus or the procedure that creates one. Accordingly, it is not unusual for a stoma to be called an ostomy (plural ostomies), as is the norm in wound, ostomy, and continence nursing.