Pulmonary fibrosis (PF) is a growing clinical problem which can result in breathlessness or respiratory failure and has an average life expectancy of 3 years from diagnosis. Therapeutic options for PF are limited and there is therefore a significant unmet clinical need. The recent resurgent interest in macrophage biology has led to a new understanding of lung macrophage origins, biology, and phenotypes. In this review we discuss fibrotic mechanisms and focus on the role of macrophages during fibrotic lung disease. Data from both human and murine studies are reviewed, highlighting novel macrophage-orientated biomarkers for disease diagnosis and potential targets for future anti-fibrotic therapies.