Do you legally have to give two weeks notice?

Two weeks notice is a custom, not a legal requirement, in nearly all US states under at-will employment. You may generally resign at any time for any reason, just as your employer may generally terminate you without notice. The exceptions matter and are worth checking: an employment contract or collective bargaining agreement can specify a notice period, some licensed professions have obligations tied to patient or client abandonment, and executives frequently have contractual notice terms tied to compensation. Outside the US, statutory notice periods are common and often substantial, so this is one of the areas where American norms are unusual rather than standard.

The practical consequences of not giving notice are real even where legal. Some employers have policies denying payout of accrued vacation to employees who leave without notice, and whether that is enforceable depends on state law, since several states treat accrued leave as earned wages that must be paid regardless. You may be marked ineligible for rehire, which surfaces in future reference checks. And in industries where everyone knows everyone, an abrupt exit follows you. The counterpoint deserves stating: notice is a courtesy that many employers do not reciprocate, and there are legitimate reasons to leave immediately, including harassment, safety, or an employer with a known practice of walking people out the moment they resign, in which case giving notice is simply choosing to lose two weeks of pay.