False dilemma, also called the either-or fallacy, us vs. them fallacy, black-or-white fallacy, false dichotomy, or the fallacy of false choice, is a mistake in logic that allows only two possibilities when more than two exist.

For example, there is "either-or fallacy" in saying that an apple must be green or red. The premise is that the apple is either one color or another; but this beginning is a mistake because some apples—not most—are other colors. In other words, most apples are red or green, but some are also yellow.