Negative mass is a theoretical concept in physics where an object would have mass with a negative value. This means that instead of being attracted to other masses, it would repel them. If negative mass existed, it could lead to unusual behaviors, such as accelerating in the opposite direction of an applied force, challenging our understanding of motion and gravity. The idea of negative mass is often discussed in the context of general relativity and quantum mechanics. While no experimental evidence has confirmed the existence of negative mass, it remains a fascinating topic for theoretical research and could have implications for concepts like dark energy and wormholes.