An optical imaging system includes a first lens having refractive power; a second lens having refractive power; a third lens having refractive power and cemented to the second lens; a fourth lens having refractive power; a fifth lens having refractive power and cemented to the fourth lens; a sixth lens having refractive power; a seventh lens having refractive power; and an eighth lens having refractive power. The first to eighth lenses are sequentially disposed in numerical order beginning with the first lens from an object side of the optical imaging system toward an imaging plane of the optical imaging system.