Temporomandibular Joint (TMJ) Disorder: This condition is a common cause of pain behind the ear due to the proximity of the TMJ to the ear and its potential to refer pain to this area. TMJ disorders can result from jaw clenching, teeth grinding, or misalignment of the jaw.

Ear Infection (Otitis Media or Otitis Externa): Infections of the middle ear or outer ear canal can cause pain that is perceived behind the ear. Symptoms may include fever, hearing loss, and discharge.
Mastoiditis: An infection of the mastoid bone, located behind the ear, which can cause pain, fever, and swelling in the area.
Tension Headache: Tension headaches can cause pain that radiates to the area behind the ear, often described as a band or a squeezing sensation around the head.
Cervicogenic Headache: Pain referred from the cervical spine can be perceived behind the ear, often associated with neck movement or strain.

Meningitis: Although less common, meningitis is a potentially life-threatening condition that can cause severe headache, fever, and neck stiffness. The pain can be referred to the area behind the ear.
Temporal Arteritis (Giant Cell Arteritis): This condition involves inflammation of the blood vessels and can cause severe headache, jaw claudication, and visual disturbances. It is a medical emergency if vision is threatened.
Stroke or Transient Ischemic Attack (TIA): While less common, pain behind the ear can be a symptom of a stroke or TIA, especially if accompanied by other neurological deficits.

Ramsay Hunt Syndrome Type 2: A rare condition caused by the varicella-zoster virus, leading to facial paralysis, ear pain, and sometimes vertigo and hearing loss.
Eagle Syndrome: A condition where an elongated styloid process or calcified stylohyoid ligament causes pain in the face and ear, often exacerbated by swallowing.
Occipital Neuralgia: Inflammation of the occipital nerves can cause severe pain that may be perceived behind the ear, often described as sharp and stabbing.