Pneumococcal disease is an infection caused by a bacterium called  Streptococcus pneumoniae (S. pneumoniae) or the pneumococcus.

Infection can be invasive and result in pneumococcal pneumonia, pneumococcal bacteremia (bacterial infection of the blood), or pneumococcal meningitis. Other common non invasive diseases are otitis media (middle-ear infection) and sinusitis.