Are there tires that never go flat?

There are tires that never go flat, often called airless tires, non-pneumatic tires, flat-free tires, or solid tires, designed to eliminate punctures and need for air pressure. These tires use solid rubber, foam-filled, or flexible spoke structures to support weight without pressurized air, so they cannot go flat from punctures, nails, or loss of air. Examples include Michelin Tweel for skid steers and lawn mowers, Amerityre flat-free tires for hand trucks, wheelbarrows, and mowers, solid rubber tires for forklifts, and airless bicycle tires like Tannus that use foam. For cars, Michelin Uptis airless prototype aims to be flat-free for passenger cars but is not yet DOT approved for highway use, though it is in testing. Benefits of never-flat tires include no flats, no need to check pressure, lower maintenance, and ability to operate over debris. Downsides include harsher ride, more vibration, higher cost, heavier weight, and limited high-speed performance. For low-speed applications like lawn mowers, golf carts, and construction equipment, flat-free tires are widely available and work well. For regular passenger cars, true never-flat airless tires are not yet widely available for highway use but are in development. So yes, tires that never go flat exist for off-road and low-speed use now.