An optical system (OL) formed from a preceding lens group (GA) having a negative refractive power, and a succeeding lens group (GB) having a positive refractive power, the lens groups being arranged in order from the object side along the optical axis. The succeeding lens group (GB) has: a focusing group (GF) having a positive refractive power, the focusing group (GF) being positioned furthest toward the object side of the succeeding lens group (GB); and an image-side group (GC) positioned further toward the image side than the focusing group (GF). During focusing from an infinitely distant object to a short-distance object, the focusing group (GF) moves toward the image side along the optical axis and satisfies the following conditional expression.

0.78<fB/fC<1.00

In this conditional expression,

fB is the focal distance of the succeeding lens group GB, and

fC is the focal distance of the image-side group GC.

An optical system (OL) formed from a preceding lens group (GA) having a negative refractive power, and a succeeding lens group (GB) having a positive refractive power, the lens groups being arranged in order from the object side along the optical axis. The succeeding lens group (GB) has: a focusing group (GF) having a positive refractive power, the focusing group (GF) being positioned furthest toward the object side of the succeeding lens group (GB); and an image-side group (GC) positioned further toward the image side than the focusing group (GF). During focusing from an infinitely distant object to a short-distance object, the focusing group (GF) moves toward the image side along the optical axis and satisfies the following conditional expression.

0.78<fB/fC<1.00

In this conditional expression,

fB is the focal distance of the succeeding lens group GB, and

fC is the focal distance of the image-side group GC.

A zoom lens includes a negative first lens group, a positive second lens group, and a subsequent lens group in order from an object side. A focusing lens group closer to an image side than the first lens group moves during focusing. The first lens group consists of a first-a lens group and a first-b lens group in order from the object side. Assuming that an average of refractive indices of the negative lenses of the first-a lens group is Nd1ave, a focal length of the focusing lens group is ff, and a focal length of the first lens group is f1, Conditional Expression (1) of 1.73<Nd1ave<1.95 and Conditional Expression (2) of 1<|ff/f1|<3 are satisfied.

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.

1.20<fLP/fL2<3.20

−3.00<fL1/fL2<−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 plurality of lens units. The plurality of lens units consist of, in order from an object side to an image side, a first lens unit having a negative refractive power, a middle group including one or more lens units, and a final lens unit having a negative refractive power. Each distance between adjacent lens units changes during zooming. The first lens unit includes at least three negative lenses. Predetermined conditions are satisfied.

A zoom lens includes a plurality of lens units. The plurality of lens units consist of, in order from an object side to an image side, a first lens unit having a negative refractive power, a middle group including one or more lens units, and a final lens unit having a negative refractive power. Each distance between adjacent lens units changes during zooming. The first lens unit includes at least three negative lenses. Predetermined conditions are satisfied.

A zoom lens includes, in order from an object side to an image side, a first lens unit having negative refractive power, a second lens unit having positive refractive power, and a rear unit including one or more lens units. A distance between adjacent lens units changes during zooming. The rear unit includes a focus lens unit having positive refractive power and configured to move from the image side to the object side during focusing from infinity to a short-distance end. The first lens unit includes, in order from the object side to the image side, a first negative lens and a second negative lens. A predetermined condition is satisfied.

A zoom lens includes, in order from an object side to an image side, a first lens unit having positive refractive power, a second lens unit having negative refractive power, and a subsequent unit including a plurality of lens units. A distance between adjacent lens units changes during zooming. The first lens unit does not move and the second lens unit moves during zooming. The first lens unit consists of, in order from the object side to the image side, a first subunit and a second subunit. The first subunit consists of two positive lenses. The second subunit consists of a single positive lens and a single negative lens. A predetermined condition is satisfied.

A projection optical system includes a first lens group having negative power, a second lens group having positive power and disposed at a reduction side of the first lens group, and a third lens group having positive power and disposed at the reduction side of the second lens group. The first lens group includes at least three negative lenses. The second lens group includes at least one positive lens. The third lens group includes a plurality of positive lenses. The at least three negative lenses of the first lens group are each a single lens. The third lens group includes a jointed lens including at least one of the plurality of positive lenses. NA is a reduction-side numerical aperture, Dst is a distortion aberration at a reduction-side maximum image height, and the projection optical system satisfies Conditional Expressions (1) and (2),
0.2<NA  (1)
−45%<Dst<−10%  (2).

A projection optical system includes a first lens group having negative power, a second lens group having positive power and disposed at a reduction side of the first lens group, and a third lens group having positive power and disposed at the reduction side of the second lens group. The first lens group includes at least three negative lenses. The second lens group includes at least one positive lens. The third lens group includes a plurality of positive lenses. The at least three negative lenses of the first lens group are each a single lens. The third lens group includes a jointed lens including at least one of the plurality of positive lenses. NA is a reduction-side numerical aperture, Dst is a distortion aberration at a reduction-side maximum image height, and the projection optical system satisfies Conditional Expressions (1) and (2),
0.2<NA  (1)
−45%<Dst<−10%  (2).