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, wherein the light emitting layer comprises a compound represented by Chemical Formula 1 below, and the electron transport region comprises a compound represented by Chemical Formula 2 below: in Chemical Formula 1, X is O, or S, L is a bond; or substituted or unsubstituted C 6-60 arylene, Ar is substituted or unsubstituted C 6-60 aryl, R and R' are each independently hydrogen; deuterium; halogen; nitrile; nitro; amino; substituted or unsubstituted C 1-60 alkyl; substituted or unsubstituted C 3-60 cycloalkyl; substituted or unsubstituted C 2-60 alkenyl group; substituted or unsubstituted C 6-60 aryl; or 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, Ar 1 and Ar 2 are each independently substituted or unsubstituted C 6-60 aryl, or 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 and L 3 are each independently substituted or unsubstituted C 6-60 arylene, i, j, and k are each independently 0, or 1, A is represented by Chemical Formula 3 below, in Chemical Formula 3, X' is Y and Z are each independently hydrogen, or deuterium, or Y and Z together form a bond; or -W-, wherein W is CR 17 R 18 , SiR 19 R 20 , NR 21 , O, or S, R 1 to R 21 are each independently hydrogen; deuterium; substituted or unsubstituted C 1-60 aryl; or substituted or unsubstituted C 2-60 heteroaryl containing at least one heteroatom selected from the group consisting of N, O and S, or two adjacent radicals of R 1 to R 21 are linked to form substituted or unsubstituted C 6-60 aryl, and one of R 1 to R 16 is linked to L 3 . 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, wherein the light emitting layer comprises a compound represented by Chemical Formula 1 below, and the electron transport region comprises a compound represented by Chemical Formula 2 below: X is O, or S, L is a bond; or substituted or unsubstituted C 6-60 arylene, Ar is substituted or unsubstituted C 6-60 aryl, R and R' are each independently hydrogen; deuterium; halogen; nitrile; nitro; amino; substituted or unsubstituted C 1-60 alkyl; substituted or unsubstituted C 3-60 cycloalkyl; substituted or unsubstituted C 2-60 alkenyl group; substituted or unsubstituted C 6-60 aryl; or 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, Ar 1 and Ar 2 are each independently substituted or unsubstituted C 6-60 aryl, or 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 and L 3 are each independently substituted or unsubstituted C 6-60 arylene, i, j, and k are each independently 0, or 1, A is represented by Chemical Formula 3 below, X' is Y and Z are each independently hydrogen, or deuterium, or Y and Z together form a bond; or -W-, wherein W is CR 17 R 18 , SiR 19 R 20 , NR 21 , O, or S, R 1 to R 21 are each independently hydrogen; deuterium; substituted or unsubstituted C 1-60 aryl; or substituted or unsubstituted C 2-60 heteroaryl containing at least one heteroatom selected from the group consisting of N, O and S, or two adjacent radicals of R 1 to R 21 are linked to form substituted or unsubstituted C 6-60 aryl, and one of R 1 to R 16 is linked to L 3 . <EOS>