An optical system includes, in order from an object side to an image side, a first lens unit, a stop, and a second lens unit. The first lens unit includes a first negative lens having a meniscus shape and a negative refractive power at a position closest to the object side and a negative lens Gn having a negative refractive power at a position closer to the image side than the first negative lens. The second lens unit includes a positive lens Gp having a positive refractive power. A material of each of the negative lens Gn and the positive lens Gp satisfies the following condition: θgF−(−0.001682·νd+0.6438)≧0.01 where “νd” denotes an Abbe number of a lens material and “θgF” denotes a relative partial dispersion with respect to g-line light and F-line light.