A capsule, in anatomy, is a cover or envelope partly or wholly surrounding a structure. Types of capsules include:

• the shell of an egg (biology)
• joint capsules – every diarthrodial joint possesses a fibrous or ligamentous capsule, lined with synovial membrane, attached to the adjacent ends of the articulating bones
• the sac which encloses the crystalline lens of the eye
• Glisson’s capsule, a thin areolar coat of fibrous tissue lying inside the tunica serosa of the liver
• Bowman’s capsules (or glomerular capsules) in the kidney substance
• the renal capsule (also known as Gerota’s fascia), a tough fibrous layer surrounding the kidney and covered in a thick layer of perinephric adipose tissue
• the suprarenal capsules, two small flattened organs in the epigastric region
• the internal, external and extreme capsules of the brain
• the outer surface of a benign tumor