In an optical system according to each exemplary embodiment, an interval between adjacent lens units changes in focusing from an infinite-distance object to a close-distance object, and a first in-focus state in which =1.2 is obtained can be caused, where is a lateral magnification of an entire system. The optical system according to each exemplary embodiment includes a plurality of focus lens units, and out of a focus lens unit having a largest absolute value of a focus sensitivity and a focus lens unit having a second largest absolute value of a focus sensitivity in a state in which focus is put on an infinite-distance object, a focus lens unit disposed on an object side is a lens unit LA, and a focus lens unit disposed on an image side is a lens unit LB. A partial optical system LC including all lenses disposed on the image side of the lens unit LB has negative refractive power. The partial optical system LC satisfies a predetermined conditional expression.

A zoom lens consists of, in order from an object side to an image side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a rear group including one or more lens units. Each distance between adjacent lens units changes during zooming. The rear group includes a focus lens unit having a positive refractive power that moves from the image side to the object side during focusing from an infinite distance object to a close distance object. A lens closest to an object in the focus lens unit has a shape with a concave surface on the object side. The following inequalities are satisfied.

[00001]$1.2<\mathrm{fLP}/\mathrm{fL}2<3.2$$-3.<\mathrm{fL}1/\mathrm{fL}2<-0.85$

fLP represents a focal length of the focus lens unit, fL1 represents a focal length of the first lens unit, and fL2 represents a focal length of the second lens unit.

A zoom lens includes a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and two or more additional lens units. In zooming, the first lens unit moves, and an interval between adjacent lens units changes. The refractive index of a negative lens A disposed on a most object side of negative lenses included in the first lens unit is higher than or equal to 1.89, and the negative lens A and a lens B disposed adjacent to an image side of the negative lens A satisfy a predetermined relationship.

A variable magnification optical system (ZL) comprises a preceding lens group (GA) having negative refractive power and a succeeding lens group (GB) having positive refractive power, which are arranged in order from the object side along an optical axis. The succeeding lens group (GB) has a focusing group (GF) and an image-side group (GC) disposed closer to the image side than the focusing group (GF), the focusing group (GF) moves to the image side along the optical axis from focusing on an object at infinity to focusing on a close-distance object, and the following conditional expression is satisfied.
1.80<fF/fBaw
FNow<3.40 where fF is the focal length of the focusing group (GF), fBaw is the focal length in the wide-angle end state of an image-side lens group (GBa) composed of lenses disposed on the image side from the focusing group (GF), and FNow is the F-number of the variable magnification optical system (ZL) in the wide-angle end state.

An optical system comprising a plurality of lens groups arranged on an optical axis and comprising a leading lens group, a first focal lens group, and a second focal lens group. The leading lens group is arranged further on the object side than the first focal lens group and the second focal lens group is arranged further on the image side than the first focal lens group. The first focal lens group has positive refractive power and moves along the optical axis to the image side when focusing from an infinite object to a short-distance object. The second focal lens group: has a negative refractive power; travels along the optical axis to the object side when focusing from an infinite object to a short-distance object; and has, between the first focal lens group and the second focal lens group, an intermediate lens group that includes at least one lens.