An imaging lens system comprising, in order from an object side to an image side: a first lens group consisting of at least one lens element (L1, L2) having negative power; a second lens group having positive power and configured with a single lens element (L2, L3); and a third lens group having power, wherein a lens element closest to the object side in the first lens group is a negative meniscus lens having a convex surface on the object side, the third lens group includes a lens element (L3, L4, L5) having positive power and a lens element (L3, L4, L5) having negative power, and conditional expressions,,, and shown below are simultaneously satisfied, − 1.2 × 10 − 5 < dn / dt pi < 0, where i ≥ 1 − 1.0 × 10 − 6 < dn / dt mi < 1.5 × 10 − 5, where i ≥ 1 − 0.2 < f / f 12 < 1.5 ν 3mi < 35, where i ≥ 1 where dn/dt pi is a relative refractive index temperature coefficient of any i-th lens element (L2-L5) having positive power included in an entire system for light in a wavelength range from 580 nm to 640 nm, inclusive, in air in a range from 0°C to 20°C, inclusive, dn/dt mi is a relative refractive index temperature coefficient of any i-th lens element (L1-L5) having negative power included in the entire system for light in a wavelength range from 580 nm to 640 nm, inclusive, in air in a range from 0°C to 20°C, inclusive, f is a focal length of the entire system at a d-line, f 12 is a composite focal length of the first lens group and the second lens group at the d-line, and v 3mi is an Abbe number at the d-line of an i-th lens element (L3-L5) having negative power included in the third lens group, wherein conditional expressions and/or shown below are further satisfied simultaneously with conditional expressions,,, and shown above, 0.58 ≤ f / f 12 < 1.5 35 < ν 1mi ≤ 59.6, where i ≥ 1 wherein v 1mi is the Abbe number at the d-line of an i-th lens element having negative power included in the first lens group. a first lens group consisting of at least one lens element (L1, L2) having negative power; a second lens group having positive power and configured with a single lens element (L2, L3); and a third lens group having power, wherein a lens element closest to the object side in the first lens group is a negative meniscus lens having a convex surface on the object side, the third lens group includes a lens element (L3, L4, L5) having positive power and a lens element (L3, L4, L5) having negative power, and conditional expressions,,, and shown below are simultaneously satisfied, − 1.2 × 10 − 5 < dn / dt pi < 0, where i ≥ 1 − 1.0 × 10 − 6 < dn / dt mi < 1.5 × 10 − 5, where i ≥ 1 − 0.2 < f / f 12 < 1.5 ν 3mi < 35, where i ≥ 1 where dn/dt pi is a relative refractive index temperature coefficient of any i-th lens element (L2-L5) having positive power included in an entire system for light in a wavelength range from 580 nm to 640 nm, inclusive, in air in a range from 0°C to 20°C, inclusive, dn/dt mi is a relative refractive index temperature coefficient of any i-th lens element (L1-L5) having negative power included in the entire system for light in a wavelength range from 580 nm to 640 nm, inclusive, in air in a range from 0°C to 20°C, inclusive, f is a focal length of the entire system at a d-line, f 12 is a composite focal length of the first lens group and the second lens group at the d-line, and v 3mi is an Abbe number at the d-line of an i-th lens element (L3-L5) having negative power included in the third lens group, wherein conditional expressions and/or shown below are further satisfied simultaneously with conditional expressions,,, and shown above, 0.58 ≤ f / f 12 < 1.5 35 < ν 1mi ≤ 59.6, where i ≥ 1 wherein v 1mi is the Abbe number at the d-line of an i-th lens element having negative power included in the first lens group. dn/dt pi is a relative refractive index temperature coefficient of any i-th lens element (L2-L5) having positive power included in an entire system for light in a wavelength range from 580 nm to 640 nm, inclusive, in air in a range from 0°C to 20°C, inclusive, dn/dt mi is a relative refractive index temperature coefficient of any i-th lens element (L1-L5) having negative power included in the entire system for light in a wavelength range from 580 nm to 640 nm, inclusive, in air in a range from 0°C to 20°C, inclusive, f is a focal length of the entire system at a d-line, f 12 is a composite focal length of the first lens group and the second lens group at the d-line, and v 3mi is an Abbe number at the d-line of an i-th lens element (L3-L5) having negative power included in the third lens group, wherein conditional expressions and/or shown below are further satisfied simultaneously with conditional expressions,,, and shown above, 0.58 ≤ f / f 12 < 1.5 35 < ν 1mi ≤ 59.6, where i ≥ 1 wherein v 1mi is the Abbe number at the d-line of an i-th lens element having negative power included in the first lens group.