To provide a wide angle optical system that has a satisfactory imaging performance and is reduced in size.

The wide angle optical system comprises, in order from the object side: a first lens 110 of negative a meniscus shape convex toward the object side; a second lens 120 of a negative meniscus shape, whose object side surface is an anamorphic surface having a horizontal curvature and a vertical curvature in a plane substantially orthogonal to an optical axis; a third positive lens 130 convex toward the object side; an aperture stop 140; and a fourth positive lens 150 convex toward the image side. If the focal distance of the entire lens system in the horizontal direction is Fh and the focal distance of the entire lens system in the vertical direction is Fv, a condition expressed by 1.10<Fv/Fh<1.30 is satisfied. A second anamorphic surface other than the object side surface of the second lens is provided in a surface having a power that is opposite in sign to the power of the object side surface of the second lens.