Neutrophil cytosolic factor 1, also known as NCF1, is a cytosolic subunit of neutrophil NADPH oxidase. NCF1, along with NCF2 and a membrane bound cytochrome b558, is required for activation of the latent NADPH oxidase necessary for superoxide production. Defects in NCF1, often resulting from recombination between NCF1 and a nearby homologous pseudogene, cause chronic granulomatous disease.