Which small, round green eggplants are commonly used in Thai green curry?

The small, round green eggplants commonly used in Thai green curry are Thai eggplants.

Thai eggplant is a cultivar of Solanum melongena, the same species as the larger purple eggplant familiar in many Western cuisines. Its small fruits are usually green and round, sometimes marked with pale stripes. Thai cooks often quarter or slice them and add them directly to curries, where their firm texture holds up in the sauce.

Green curry originated in central Thailand and typically combines coconut milk, green-chile curry paste, fish sauce, palm sugar, herbs, and a protein such as chicken or fish. Thai eggplant is a common vegetable addition, along with pea eggplant and Thai basil. The eggplant absorbs the aromatic coconut-based sauce while contributing a mildly bitter flavor.

A common mix-up is confusing Thai eggplant with pea eggplant. Both can appear in green curry, but pea eggplant is much smaller and grows in clusters resembling peas. Okra and zucchini may appear in modern adaptations, but they are not the canonical answer to this question.