A laparotomy is a surgical maneuver involving an incision through the abdominal wall to gain access into the abdominal cavity. It is also known as coeliotomy.

In a diagnostic laparotomy, the nature of the disease is unknown, and laparotomy is deemed the best way to identify the cause. In therapeutic laparotomy, a cause has been identified (e.g. peptic ulcer, colon cancer) and laparotomy is required for its therapy. Usually, only diagnostic laparotomy is referred as a surgical operation by itself; and when a specific operation is already planned, laparotomy is considered merely the first step of the procedure.

Depending on incision placement, it may give access to any abdominal organ or space, and is the first step in any major diagnostic or therapeutic surgical procedure of these organs, which include:

• the lower part of the digestive tract (the stomach, duodenum, jejunum, ileum and colon)
• the liver, pancreas and spleen
• the bladder
• the female reproductive organs (the uterus and ovaries)
• the retroperitoneum (the kidneys, the aorta, abdominal lymph nodes)

The most common incision for laparotomy is the midline incision, a vertical incision which follows the linea alba. The upper midline incision usually extends from the from the xiphoid process to the umbilicus, while a typical lower midline incision is limited by the umbilicus superiorly and by the pubic symphysis inferiorly. Sometimes a single incision extending from xiphoid process to pubic symphysis is employed, especially in trauma surgery . Midline incisions are particularly favoured in diagnostic laparotomy, as they allow wide access to most of the abdominal cavity.

Other common laparotomy incisions include:

• the Kocher (right subcostal) incision (after Emil Theodor Kocher); appropriate for operations on the liver, gallbladder and biliary tract;
• the Davis or Davis-Rockey "muscle-splitting" right lower quadrant incision for appendectomy;
• the Pfannenstiel incision, a transverse incision below the umbilicus and just above the pubic symphysis, most often employed for cesarean section;
• Lombotomy consists of a lumbar incision which permits access to the kidneys (which are retroperitoneal) without entering the peritoneal cavity. It is a common operative approach in renal surgery.

A related procedure is laparoscopy, where cameras and other instruments are inserted into the peritoneal cavity via small holes in the abdomen. For example, an appendectomy can be done either by a laparotomy or by an laparoscopic access.