Heteroaryl substituents are important building blocks of functionalized organic compounds in drug discovery, materials science, and catalysis. Quantitative descriptions of steric and electronic properties of heteroaryl substituents are essential in establishing structure-activity relationships and predicting reactivity and properties of heteroaromatic compounds. Here, we introduce HArD, a database of heteroaryl descriptors, that comprises density functional theory (DFT)-computed steric and electronic descriptors of 31,500 heteroaryl substituents. The database features heteroaryl substituents comprising 5- and 6-membered rings as well as 5,6- and 6,6-fused ring systems with C, N, O, and S atoms. Different regioisomers and additional substituents on heteroaromatic rings were included to describe the diverse property space of heteroaryl substituents. The database includes 66 descriptors such as buried volume and Sterimol parameters to describe steric effects, atomic charges and HOMO/LUMO coefficients and energies to describe electronic effects, and Harmonic Oscillator Model of Aromaticity (HOMA) values describing aromaticity. In addition, we developed Hammett-type heteroaryl substituent constants (σ_Het) based on computed heteroaryl carboxylic acid pK_a values, which aim to extend the broadly used Hammett parameters (σ_p) and (σ_m) from substituted phenyl groups to substituted heteroaryl groups. The database covers monosubstituted derivatives incorporating any of the functional groups NMe₂, NH₂, OH, OMe, Me, TMS, F, Cl, Br, Ac, CN, and NO₂.