There are some colleges and majors where it’s possible to graduate in 3 years with good planning, some luck, and exceptional time management skills.
There are some colleges and majors where it is very, very difficult. A Dean won’t waive a pre-requisite but the sequencing of the courses means that you can’t take what you need to take when you want to take it. A committee evaluates your placement test and concludes that you are NOT ready to move to the next level even if you got an A in what you think is a similar class in HS.
And there are some fields where even if it’s possible, it’s a bad idea. If you are applying to competitive grad programs with 25% less than everyone else (fewer internships, research roles, fewer professors to write you a recommendation or pick up the phone on your behalf, much less networking in fields where that’s important), etc. Or for getting a fulltime job- same issues.
Why do you want to graduate early?