Stand Your Ground Act of 2021 This bill establishes affirmative defenses for individuals who use (or threaten or attempt to use) force in the commission of certain federal criminal violations. First, an individual is justified in using (or threatening or attempting to use) non-deadly force if the individual reasonably believes it is necessary to defend against an imminent use of unlawful force. An individual who uses or threatens to use non-deadly force in accordance with this affirmative defense does not have a duty to retreat before using or threatening to use such force. Second, an individual is justified in using (or threatening or attempting to use) deadly force if the individual reasonably believes it is necessary to prevent imminent death or great bodily harm or to prevent the imminent commission of a forcible felony. An individual who uses, threatens, or attempts to use deadly force in accordance with this affirmative defense does not have a duty to retreat and has the right to stand his or her ground so long as the individual is not engaged in a criminal activity and is in a place where he or she has a right to be.