An organometallic compound represented by Formula 1, wherein M 1 is beryllium, magnesium, aluminum, calcium, titanium, manganese, cobalt, copper, zinc, gallium, germanium, zirconium, ruthenium, rhodium, palladium, silver, rhenium, platinum, or gold; A 1 to A 3 are each independently a C 5 -C 30 carbocyclic group or a C 1 -C 30 heterocyclic group; A 4 is a 5-membered heterocyclic group; A 5 is a C 7 -C 30 carbocyclic group of at least two rings comprising a 6-membered carbocyclic group, or A 5 is a C 1 -C 30 heterocyclic group of at least two rings comprising a 6-membered carbocyclic group or a 6-membered heterocyclic group; X 10 , X 20 , X 30 , and X 40 to X 44 are each independently C or N; T 1 to T 3 are each independently a single bond, *-N[(L 1 ) a1 -(R 1 ) b1 ]-*', *-B(R 1 )-*', *-P(R 1 )-*', *-C(R 1 )(R 2 )-*', *-Si(R 1 )(R 2 )-*', *-Ge(R 1 )(R 2 )-*', *-S-*', *-Se-*', *-O-*', *-C(=O)-*', *-S(=O)-*', *-S(=O) 2 -*', *-C(R 1 )=C(R 2 )-*', *-C(=S)-*', or *-C≡C-*'; and wherein the other substituents may be understood by referring to the detailed description.