Isoindoline is a heterocyclic organic compound with the molecular formula C8H9N.

Isoindoline itself is not commonly encountered, but several derivatives are found in nature and some synthetic derivatives are commercially valuable drugs, e.g. lenalidomide and pazinaclone.

Isoindolylcarboxylic acid and 1,3-disubstituted isoindolines are constituents of some pharmaceuticals and natural products.

Isoindolines can be prepared by 1,2-addition of a nucleophile onto a bifunctional ε-benzoiminoenoates followed by intramolecular aza-Michael reaction.

Another route involves [3+2] cycloaddition of the azomethine ylides (e.g. (CH2)2NR) to quinone in the presence of suitable catalysts.