This document provides an overview of interstitial lung disease (ILD). ILD involves the lung parenchyma between the alveoli and small airways. There are over 200 known ILDs classified into groups based on predominant inflammation/fibrosis or granulomatous reaction. Idiopathic pulmonary fibrosis is the most common ILD and has a poor prognosis. Diagnosis involves clinical history, imaging like HRCT, pulmonary function tests showing restriction, and sometimes lung biopsy. Management focuses on identifying and removing causes, suppressing inflammation, and lung transplantation for severe cases.