An organometallic compound represented by Formula 1, wherein M1 is beryllium, magnesium, aluminum, calcium, titanium, manganese, cobalt, copper, zinc, gallium, germanium, zirconium, ruthenium, rhodium, palladium, silver, rhenium, platinum, or gold; A1 to A3 are each independently a C5-C30 carbocyclic group or a C1-C30 heterocyclic group; A4 is a 5-membered heterocyclic group; A5 is at least two rings of a C7-C30 carbocyclic group comprising a 6-membered carbocyclic group, or A5 is at least two rings of a C1-C30 heterocyclic group comprising a 6-membered carbocyclic group or a 6-membered heterocyclic group; X10, X20, X30, and X40 to X44 are each independently C or N; T1 to T3 are each independently a single bond, *—N[(L1)a1-(R1)b1]—*′, *—B(R1)—*′, *—P(R1)—*′, *—C(R1)(R2)—*′, *—Si(R1)(R2)—*′, *—Ge(R1)(R2)—*′, *—S—*′, *—Se—*′, *—O—*′, *—C(═O)—*′, *—S(═O)—*′, *—S(═O)2—*′, *—C(R1)═C(R2)—*′, *—C(═S)—*′, or *—C≡C—*′; and wherein the other substituents may be understood by referring to the detailed description.