Ultra vires is a Latin phrase meaning "beyond the powers". If an act requires legal authority and it is done with such authority, it is characterised in law as intra vires ("within the powers"). If it is done without such authority, it is ultra vires. Acts that are intra vires may equivalently be termed "valid" and those that are ultra vires "invalid".
In corporate law, ultra vires describes acts attempted by a corporation that are beyond the scope of powers granted by the corporation's objects clause, articles of incorporation or in a clause in its Bylaws, in the laws authorizing a corporation's formation, or similar founding documents. Acts attempted by a corporation that are beyond the scope of its charter are void or voidable.