Aspirin damages what organ?

Aspirin (acetylsalicylic acid) can damage the stomach lining, leading to gastritis, ulcers, and gastrointestinal bleeding—so the organ most commonly associated with aspirin-induced injury is the stomach (GI tract) [1].

It can also affect the kidneys (especially with dehydration or long-term/high-dose use), but the classic “damaged organ” in most basic health explanations is the stomach [1].

Sources:
[1] https://www.nhs.uk/medicines/aspirin/