The largest bird that cannot fly is the ostrich. Native to Africa, ostriches are the world's heaviest birds, with adults weighing up to 350 pounds and standing about 9 feet tall. Their large wings are not suited for flight, but they are adapted for running, capable of reaching speeds up to 45 miles per hour. Ostriches are also known for their powerful legs, which they can use to deliver strong kicks against predators. Besides their impressive size and speed, these flightless birds are characterized by their long necks, long legs, and distinctive plumage, making them a unique species in the avian world.