特發性肺纖維化(Idiopathic pulmonary fibrosis, IPF)是最常見的一種特發性間質性肺炎(Idiopathic interstitial pneumonia, IIP)。特發性間質性肺炎(IIP)，又稱非感染性肺炎，是一群病因不明的瀰漫性間質肺病，除了特發性肺纖維化外，還包括：非特異性間質性肺炎nonspecific interstitial pneumonia (NSIP)、脫屑性間質性肺炎desquamative interstitial pneumonia (DIP), respiratory bronchiolitis associated interstitial lung disease (RBILD), acute interstitial pneumonia (AIP), 淋巴樣間質性肺炎lymphocytic interstitial pneumonia (LIP), 和cryptogenic organizing pneumonia (COP)。