A polycyclic compound represented by Formula 1: wherein, in Formula 1, X 1 is C, Si, or Ge, Ar is a substituted or unsubstituted aryl group having 6 to 30 carbon atoms for forming a ring, or a substituted or unsubstituted heteroaryl group having 2 to 30 carbon atoms for forming a ring, R 1 to R 4 are each independently a hydrogen atom, a deuterium atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms for forming a ring, or a substituted or unsubstituted heteroaryl group having 2 to 30 carbon atoms for forming a ring, "a" to "d" are each independently an integer of 0 to 4, and AC is represented by one of Formulae 5 to 7: wherein, in Formula 7, A 1 to A 13 are each independently N or CR 15, at least one of A 1 to A 8 is N, at least one of A 9 to A 13 is N, and at least one of A 1 to A 13 is a part that is connected with Formula 1, and R 15 a hydrogen atom, a deuterium atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms for forming a ring, or a substituted or unsubstituted heteroaryl group having 2 to 30 carbon atoms for forming a ring. wherein, in Formula 1, X 1 is C, Si, or Ge, Ar is a substituted or unsubstituted aryl group having 6 to 30 carbon atoms for forming a ring, or a substituted or unsubstituted heteroaryl group having 2 to 30 carbon atoms for forming a ring, R 1 to R 4 are each independently a hydrogen atom, a deuterium atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms for forming a ring, or a substituted or unsubstituted heteroaryl group having 2 to 30 carbon atoms for forming a ring, "a" to "d" are each independently an integer of 0 to 4, and AC is represented by one of Formulae 5 to 7: X 1 is C, Si, or Ge, Ar is a substituted or unsubstituted aryl group having 6 to 30 carbon atoms for forming a ring, or a substituted or unsubstituted heteroaryl group having 2 to 30 carbon atoms for forming a ring, R 1 to R 4 are each independently a hydrogen atom, a deuterium atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms for forming a ring, or a substituted or unsubstituted heteroaryl group having 2 to 30 carbon atoms for forming a ring, "a" to "d" are each independently an integer of 0 to 4, and AC is represented by one of Formulae 5 to 7: wherein, in Formula 7, A 1 to A 13 are each independently N or CR 15, at least one of A 1 to A 8 is N, at least one of A 9 to A 13 is N, and at least one of A 1 to A 13 is a part that is connected with Formula 1, and R 15 a hydrogen atom, a deuterium atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms for forming a ring, or a substituted or unsubstituted heteroaryl group having 2 to 30 carbon atoms for forming a ring. A 1 to A 13 are each independently N or CR 15, at least one of A 1 to A 8 is N, at least one of A 9 to A 13 is N, and at least one of A 1 to A 13 is a part that is connected with Formula 1, and R 15 a hydrogen atom, a deuterium atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms for forming a ring, or a substituted or unsubstituted heteroaryl group having 2 to 30 carbon atoms for forming a ring.