Under Illinois law, the age of consent for any type of sexual activity is, typically, 17 years. This means anyone younger than 17 years of age cannot lawfully consent to any type of sex act involving sexual conduct. Sexual conduct is the touching of any sex organ of another.

Is a 16 year old dating a 18 legal in Illinois?

It is illegal for a 16 year old to have a sexual relationship with anyone 18 or older. Parent or individual consent is irrelevant because as accurately stated above, you cannot consent to an illegal act.