At-will employment means that either the employer or the employee can end the employment relationship at any time, for any reason (or no reason), with or without notice. It is the default employment arrangement in every U.S. state except Montana.
What this means for employers: They can terminate employees without needing to show "cause" or provide advance notice (unless there's a contract stating otherwise).
What this means for employees: You can quit at any time without legal consequences (though professional courtesy suggests giving 2 weeks' notice).
Important exceptions to at-will:
Discrimination: Employers cannot fire you based on race, sex, religion, age, disability, or other protected characteristics.
Retaliation: You cannot be fired for exercising legal rights — filing a workers' comp claim, reporting safety violations, taking FMLA leave, or whistleblowing.
Public policy: Most states prohibit firing for reasons that violate public policy — refusing to commit an illegal act, serving jury duty, or voting.
Contract exception: If you have a written employment contract or collective bargaining agreement, its terms override at-will status.
Implied contract: Some courts have found that employee handbooks, verbal promises, or consistent company practices can create implied contracts that limit at-will termination.