An organic light emitting device comprising: an anode; a cathode; a light emitting layer disposed between the anode and the cathode; and an electron transport region between the cathode and the light emitting layer, characterized in that the light emitting layer includes a compound represented by Chemical Formula 1 below, and the electron transport region includes a compound represented by Chemical Formula 2 below: in Chemical Formula 1, X is O or S, L is a bond; or a substituted or unsubstituted C 6-60 arylene, Ar is a substituted or unsubstituted C 6-60 aryl, R and R' are each independently hydrogen; deuterium; a halogen; a cyano; a nitro; an amino; a substituted or unsubstituted C 1-60 alkyl; a substituted or unsubstituted C 3-60 cycloalkyl; a substituted or unsubstituted C 2-60 alkenyl group; a substituted or unsubstituted C 6-60 aryl; or a substituted or unsubstituted C 2-60 heteroaryl containing at least one heteroatom selected from the group consisting of N, O, and S, n1 is an integer of 0 to 3, and n2 is an integer of 0 to 4, in Chemical Formula 2, R 1 and R 2 are each independently a substituted or unsubstituted C 6-60 aryl, or a substituted or unsubstituted C 2-60 heteroaryl containing at least one heteroatom selected from the group consisting of N, O, and S, L 1, L 2, L 3, and L 4 are each independently a bond; or a substituted or unsubstituted C 6-60 arylene, A is a substituted or unsubstituted naphthylene, B is a C 6-60 aryl substituted with at least one cyano group; or a substituted or unsubstituted C 2-60 heteroaryl containing 1 to 3 nitrogen atoms, and i, j, k, and I are each independently 0 or 1. an anode; a cathode; a light emitting layer disposed between the anode and the cathode; and an electron transport region between the cathode and the light emitting layer, characterized in that the light emitting layer includes a compound represented by Chemical Formula 1 below, and the electron transport region includes a compound represented by Chemical Formula 2 below: in Chemical Formula 1, X is O or S, L is a bond; or a substituted or unsubstituted C 6-60 arylene, Ar is a substituted or unsubstituted C 6-60 aryl, R and R' are each independently hydrogen; deuterium; a halogen; a cyano; a nitro; an amino; a substituted or unsubstituted C 1-60 alkyl; a substituted or unsubstituted C 3-60 cycloalkyl; a substituted or unsubstituted C 2-60 alkenyl group; a substituted or unsubstituted C 6-60 aryl; or a substituted or unsubstituted C 2-60 heteroaryl containing at least one heteroatom selected from the group consisting of N, O, and S, n1 is an integer of 0 to 3, and n2 is an integer of 0 to 4, in Chemical Formula 2, R 1 and R 2 are each independently a substituted or unsubstituted C 6-60 aryl, or a substituted or unsubstituted C 2-60 heteroaryl containing at least one heteroatom selected from the group consisting of N, O, and S, L 1, L 2, L 3, and L 4 are each independently a bond; or a substituted or unsubstituted C 6-60 arylene, A is a substituted or unsubstituted naphthylene, B is a C 6-60 aryl substituted with at least one cyano group; or a substituted or unsubstituted C 2-60 heteroaryl containing 1 to 3 nitrogen atoms, and i, j, k, and I are each independently 0 or 1. X is O or S, L is a bond; or a substituted or unsubstituted C 6-60 arylene, Ar is a substituted or unsubstituted C 6-60 aryl, R and R' are each independently hydrogen; deuterium; a halogen; a cyano; a nitro; an amino; a substituted or unsubstituted C 1-60 alkyl; a substituted or unsubstituted C 3-60 cycloalkyl; a substituted or unsubstituted C 2-60 alkenyl group; a substituted or unsubstituted C 6-60 aryl; or a substituted or unsubstituted C 2-60 heteroaryl containing at least one heteroatom selected from the group consisting of N, O, and S, n1 is an integer of 0 to 3, and n2 is an integer of 0 to 4, in Chemical Formula 2, R 1 and R 2 are each independently a substituted or unsubstituted C 6-60 aryl, or a substituted or unsubstituted C 2-60 heteroaryl containing at least one heteroatom selected from the group consisting of N, O, and S, L 1, L 2, L 3, and L 4 are each independently a bond; or a substituted or unsubstituted C 6-60 arylene, A is a substituted or unsubstituted naphthylene, B is a C 6-60 aryl substituted with at least one cyano group; or a substituted or unsubstituted C 2-60 heteroaryl containing 1 to 3 nitrogen atoms, and i, j, k, and I are each independently 0 or 1.