In November 2024, a four-legged robot ran a full marathon in Sangju, South Korea, on a single battery. It covered 42.195 kilometers in 4 hours, 19 minutes, and 52 seconds, with no recharge and no battery swap. The robot, RAIBO2, finished among human runners on a hilly course with 286 meters of elevation change.
On September 23, 2026, a KAIST team led by Jemin Hwangbo published the result in Nature. Four-legged robots have often been limited to about 20 kilometers on one charge. RAIBO2 traveled about three times as far, per charge, as existing machines of its kind. Researchers say it is the first quadruped, a four-legged robot, to finish an official full marathon without changing its battery.
The point was not a bigger pack of cells. Standing and stepping already burn energy in the joints. Hwangbo's group lightened the legs, improved the motor circuits, and used machine learning to cut waste in each step. After the finish, the robot had used 1,280 watt-hours of a 2,016 watt-hours battery. The team estimates it could have gone about 25 kilometers more.
Its cost of transport, the energy used to move each unit of weight each meter, was 0.25, below a common human figure of 0.37. That is a measure of efficiency, not speed. The clock showed how long the battery lasted, not that the robot beat ordinary runners.
Hwangbo said RAIBO2 was not a machine that simply ran farther by carrying a larger battery. The whole robot was redesigned so more of the stored energy became actual distance. The marathon data, he said, show how a four-legged robot should be built if it is to work for hours outdoors.
Rescue work in hills and disaster zones has long been held back by short battery life. A dog-shaped machine that can keep moving for a marathon's worth of ground, without a pit stop, brings that work a step closer.