A hot-rolled steel sheet having a maximum tensile strength of 980 MPa or more and an excellent low temperature toughness, which comprises: a chemical composition consisting of, in mass%, C: 0.01 to 0.2%; Si: 0.001 to 2.5%; Mn: 1 to 4.0%; P: 0.10% or less; S: 0.03% or less; Al: 0.001 to 2.0%; N: 0.0005 to 0.01%; O: 0.001 to 0.01%; and Ti: 0.03 to 0.30%; optionally one or more of Nb: 0.01 to 0.30%; Cu: 0.01 to 2.0%; Ni: 0.01 to 2.0%; Mo: 0.01 to 1.0%; V: 0.01 to 0.3%; Cr: 0.01 to 2.0%; Mg: 0.0005 to 0.01%; Ca: 0.0005 to 0.01%; REM: 0.0005 to 0.1%; B: 0.0002 to 0.01%; and optionally further 1% or less in total of one type or two or more types selected from the group consisting of Zr, Sn, Co, Zn, and W; and the balance being composed of iron and impurities; and a structure comprising tempered martensite or a mixed structure of tempered martensite and lower bainite, in which by volume fraction, 90% or more of the tempered martensite, or by volume fraction, 90% or more in total of both the tempered martensite and the lower bainite is contained and an average aspect ratio of the tempered martensite and the lower bainite is 2 or less; wherein an effective crystal grain diameter of the tempered martensite and the lower bainite is 10 μm or less; and wherein 1 × 10 6 (pieces/mm 2) or more of iron-based carbides exist in the tempered martensite and the lower bainite, wherein the steel sheet having a maximum tensile strength of 980 MPa or more indicates a steel sheet whose maximum tensile stress measured by a tensile test performed in conformity with JIS Z 2241 by using a JIS No. 5 test piece cut out in a vertical direction relative to the rolling direction of hot rolling is 980 MPa or more, and wherein the steel sheet having an excellent low temperature toughness indicates a steel sheet whose fracture appearance transition temperature (vTrs) of a Charpy test performed in conformity with JIS Z 2242 is -40°C or lower. a chemical composition consisting of, in mass%, C: 0.01 to 0.2%; Si: 0.001 to 2.5%; Mn: 1 to 4.0%; P: 0.10% or less; S: 0.03% or less; Al: 0.001 to 2.0%; N: 0.0005 to 0.01%; O: 0.001 to 0.01%; and Ti: 0.03 to 0.30%; C: 0.01 to 0.2%; Si: 0.001 to 2.5%; Mn: 1 to 4.0%; P: 0.10% or less; S: 0.03% or less; Al: 0.001 to 2.0%; N: 0.0005 to 0.01%; O: 0.001 to 0.01%; and Ti: 0.03 to 0.30%; optionally one or more of Nb: 0.01 to 0.30%; Cu: 0.01 to 2.0%; Ni: 0.01 to 2.0%; Mo: 0.01 to 1.0%; V: 0.01 to 0.3%; Cr: 0.01 to 2.0%; Mg: 0.0005 to 0.01%; Ca: 0.0005 to 0.01%; REM: 0.0005 to 0.1%; B: 0.0002 to 0.01%; and Nb: 0.01 to 0.30%; Cu: 0.01 to 2.0%; Ni: 0.01 to 2.0%; Mo: 0.01 to 1.0%; V: 0.01 to 0.3%; Cr: 0.01 to 2.0%; Mg: 0.0005 to 0.01%; Ca: 0.0005 to 0.01%; REM: 0.0005 to 0.1%; B: 0.0002 to 0.01%; and optionally further 1% or less in total of one type or two or more types selected from the group consisting of Zr, Sn, Co, Zn, and W; and the balance being composed of iron and impurities; and a structure comprising tempered martensite or a mixed structure of tempered martensite and lower bainite, in which by volume fraction, 90% or more of the tempered martensite, or by volume fraction, 90% or more in total of both the tempered martensite and the lower bainite is contained and an average aspect ratio of the tempered martensite and the lower bainite is 2 or less; wherein an effective crystal grain diameter of the tempered martensite and the lower bainite is 10 μm or less; and wherein 1 × 10 6 (pieces/mm 2) or more of iron-based carbides exist in the tempered martensite and the lower bainite, wherein the steel sheet having a maximum tensile strength of 980 MPa or more indicates a steel sheet whose maximum tensile stress measured by a tensile test performed in conformity with JIS Z 2241 by using a JIS No. 5 test piece cut out in a vertical direction relative to the rolling direction of hot rolling is 980 MPa or more, and wherein the steel sheet having an excellent low temperature toughness indicates a steel sheet whose fracture appearance transition temperature (vTrs) of a Charpy test performed in conformity with JIS Z 2242 is -40°C or lower.