Is it safe to eat chicken that has been marinating for 3 days?

It's generally not safe to eat chicken that has been marinating for 3 days, especially if it's been stored in the refrigerator. The USDA recommends marinating chicken for no more than 2 days to prevent bacterial growth. If the chicken has been kept at a constant, safe temperature (below 40°F), it may still be okay, but it's best to use your judgment and consider any off smells or changes in texture. When in doubt, it's safer to discard it.