Sjögren syndrome or Sjögren's syndrome (SjS, SS) is a long-term autoimmune disease that affects the body's moisture-producing (lacrimal and salivary) glands, and often seriously affects other organ systems, such as the lungs, kidneys, and nervous system. Primary symptoms are dryness (dry mouth and dry eyes), pain and fatigue. Other symptoms can include dry skin, vaginal dryness, a chronic cough, numbness in the arms and legs, feeling tired, muscle and joint pains, and thyroid problems. Those affected are also at an increased risk (15%) of lymphoma.

While the exact cause is unclear, it is believed to involve a combination of genetics and an environmental trigger such as exposure to a virus or bacterium. It can occur independently of other health problems (primary Sjögren's syndrome) or as a result of another connective tissue disorder (secondary Sjögren's syndrome). Sjögren's syndrome may be associated with other autoimmune diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) or systemic sclerosis. The inflammation that results progressively damages the glands. Diagnosis is by biopsy of moisture-producing glands and blood tests for specific antibodies. On biopsy there are typically lymphocytes within the glands.

While Sjögren's syndrome is one of the most common auto-immune diseases, it has no specific and non-invasive diagnostic tests and treatment is directed at managing the person's symptoms. For dry eyes, artificial tears, medications to reduce inflammation, punctal plugs, or surgery to shut the tear ducts may be tried. For a dry mouth, chewing gum (preferably sugar-free), sipping water, or a saliva substitute may be used. In those with joint or muscle pain, ibuprofen may be used. Medications that can cause dryness, such as antihistamines, may also be stopped. The most specific extant diagnostic test requires lip biopsy.

The disease was described in 1933 by Henrik Sjögren, after whom it is named; however, a number of earlier descriptions of people with the symptoms exist. Between 0.2 and 1.2% of the population is affected, with half having the primary form and half the secondary form. It is around 10 times more common in women than in men. Though the disease commonly begins in middle age, anyone can be affected. Among those without other autoimmune disorders, life expectancy is unchanged.