A photographing lens system comprising eight lens elements (E1, E2, E3, E4, E5, E6, E7, E8), the eight lens elements (E1, E2, E3, E4, E5, E6, E7, E8) being, in order from an object side to an image side along an optical path, a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, a sixth lens element, a seventh lens element and an eighth lens element, each of the eight lens elements (E1, E2, E3, E4, E5, E6, E7, E8) having an object-side surface facing toward the object side and an image-side surface facing toward the image side, and a total number of the lens elements (E1, E2, E3, E4, E5, E6, E7, E8) of the photographing lens system is eight; wherein the first lens element has positive refractive power, the object-side surface of the first lens element is convex in a paraxial region thereof, the image-side surface of the first lens element is concave in a paraxial region thereof, the second lens element has negative refractive power, the object-side surface of the second lens element is convex in a paraxial region thereof, the image-side surface of the second lens element is concave in a paraxial region thereof, the fifth lens element has positive refractive power, the seventh lens element has negative refractive power, the image-side surface of the seventh lens element is concave in a paraxial region thereof and has at least one convex critical point in an off-axis region thereof, the object-side surface of the eighth lens element is convex in a paraxial region thereof and has at least one concave critical point in an off-axis region thereof, the image-side surface of the eighth lens element is concave in a paraxial region thereof and has at least one convex critical point in an off-axis region thereof, and the image-side surface of the eighth lens element has at least one inflection point; wherein a focal length of the photographing lens system is f, a focal length of the seventh lens element is f7, a focal length of the eighth lens element is f8, an axial distance between the object-side surface of the first lens element and an image surface is TL, a maximum image height of the photographing lens system is ImgH, a curvature radius of the object-side surface of the sixth lens element is R11, and the following conditions are satisfied: − 0.30 < f / f 8 < 5.0; 0.50 < TL / ImgH < 1.70; and characterized in that the following conditions are satisfied: − 2.30 < f / f 7 ≤ − 0.99; − 3.0 < f / R 11 < 0.25. wherein the first lens element has positive refractive power, the object-side surface of the first lens element is convex in a paraxial region thereof, the image-side surface of the first lens element is concave in a paraxial region thereof, the second lens element has negative refractive power, the object-side surface of the second lens element is convex in a paraxial region thereof, the image-side surface of the second lens element is concave in a paraxial region thereof, the fifth lens element has positive refractive power, the seventh lens element has negative refractive power, the image-side surface of the seventh lens element is concave in a paraxial region thereof and has at least one convex critical point in an off-axis region thereof, the object-side surface of the eighth lens element is convex in a paraxial region thereof and has at least one concave critical point in an off-axis region thereof, the image-side surface of the eighth lens element is concave in a paraxial region thereof and has at least one convex critical point in an off-axis region thereof, and the image-side surface of the eighth lens element has at least one inflection point; wherein a focal length of the photographing lens system is f, a focal length of the seventh lens element is f7, a focal length of the eighth lens element is f8, an axial distance between the object-side surface of the first lens element and an image surface is TL, a maximum image height of the photographing lens system is ImgH, a curvature radius of the object-side surface of the sixth lens element is R11, and the following conditions are satisfied: − 0.30 < f / f 8 < 5.0; 0.50 < TL / ImgH < 1.70; and characterized in that the following conditions are satisfied: − 2.30 < f / f 7 ≤ − 0.99; − 3.0 < f / R 11 < 0.25.